I know 5th Cing is a thing, so my point is that there are ways to exploit the system by joining the other side and behaving the opposite of what is expected in some way.
Not many are going to be so foolish as to say 'No'. But there are a number of factors that serve to reduce the incentive to 5C, and in combination they likely drive it to near-extinction. Low-level situational-5C is an accommodatable part of a conflict between factions,
IF the mechanics that enable it are suitably balanced.
Was anything included in the proposal to stop 5th columning?
TL;DR: Yes.
Background:
At the moment, in-game, every single element is inadvertently biased towards benefiting 5C. It is
always far harder to oppose it, than to do it. Other forms of attack do require more prep, more manpower, more grind, are more uncertain to succeed, and have nothing like the lasting impact. 5C expansions are extremely difficult to undo, and if they are even possible, often require a wider community effort, with cooperation or at least taking advantage, from enemies, in order to shed them. It is fair to say that shedding bad systems requires a Power to ritually disembowel itself by self-underming & turmoiling itself. It has to do what it's enemies have always been trying to do. Shedding 5C systems, is more like ritually hanging-drawing & then quartering yourself, because those 5C systems are so far down the order of systems that will shed. Devising a strategy to achieve that, and fight your way out of the resultant mess.. You can see why 5C has far too much incentive at present.
This is inevitably gonna be TL;DR but you better read it cause you did ask. xD
Rubbernuke's proposals are built around Sandro's Flash Topic from May 2018, so i'll start there..
"Vote to veto preparation
• Each player can vote to veto or support each preparation
• If a preparation ends the cycle with more veto votes than support votes it is removed from preparation
• Voting requires minimum, rolling time spent pledged and active for a power, somewhere into rank 2
Reasoning: these two changes in tandem are meant to make it easier to prevent bad systems from being prepared with minimal effort. Rather than use consolidation, which must be chosen blind in terms of both the final preparation for systems and the final resting place for the consolidation marker, here Commanders are voting on a fixed list and can choose precisely which systems they want to attempt to veto.
Profitability modifier applied to votes and preparation successes
• A system’s base profitability modifies preparation votes, withdraw votes and preparation successes
• Votes and successes for profitable systems are increased by a factor of 10
Reasoning: we think this modifier acts as another barrier against internal sabotage, forcing the saboteurs to work many more times harder to get the same effect as a Commander who has the power’s interests at heart.
Open only
• Powerplay contacts are only available to players in open
• Powerplay vouchers and commodities are destroyed if a player enters solo or private groups
Reasoning: We’ve saved the biggest change for last, as making Powerplay Open only goes way beyond the remit of a tweak. We’ve seen this topic discussed many times and we think it’s time we addressed it directly to get as much quality feedback as possible.
Powerplay is fundamentally about consensual player versus player conflict. We think that pretty much all of the systems and rules would benefit from being played out in Open only, as it would dramatically increase the chance of meeting other pledged players and being able to directly affect the outcomes of power struggles."
Source:
Frankly, depending on the details of the final implementation, I think those measures provide an elegant simple solution that would be sufficient regards 5C.
In Rubbernuke's (most recent) proposal (linked in the OP), the above "Vote to Veto prep" and "Open only" elements are modified, but do not reduce anti-5C measures at all. Overall it is a belt & braces, cast-iron Anti-5C list.
Trust
Powerplay players have a new variable to manage- 'Trust'. It acts similar to rep with factions and replaces personal merits. The more positive outcomes you have doing tasks across all modes, the higher this value gets. It acts as a multiplier for rewards, as well as your allocation (see later sections for details).
The trust value ranges from 10 (maximum) to -9 (no trust) depending on activity. At full trust (10) all personal perks are unlocked in a similar way to rank 5 currently. But, if your trust gets too low through failing certain tasks repeatedly, you are automatically unpledged and treated as a defector- i.e. that power sends assassins after you.
Automatic unpledging occurs after 1 BGS 'tick' at -9. This is an anti 5C measure, so that positive actions reward, while being 5C gets you kicked out and punished (see later for examples of this in action).
TL;DR : 5C got curb-stomped.
Voting
Along with Sandros weighting a pledge can only vote if their trust value is 9 or 10. This makes 5C have to improve the power to be able to vote, which is hard if through exploitative play they get a low trust score as outlined. A regular player who is delivering, running missions that improve the power will always have a high trust value.
Your vote also counts towards trust. The lower the CC of the system you are voting for, the more your trust is knocked. So vote for a wildly negative one, and prepare to take the hit.
TL;DR : After curbstomp, 5C got a blood-eagle. (can't be too careful)
In practice with 5C
Voting for negative CC systems, delivering preparation merits to 5C systems, shooting your own Powers ships, fortifying systems past 100% all affect your trust score to varying degrees. However it is possible that if a 5C agent keeps on making 5C moves they will be unpledged within one tick and expelled for 2 whole cycles, making direct 5C very hard to do for any length of time. This also stops multiple 'alt' accounts doing the same.
TL;DR : 5C carcass got burnt, sealed in a lead-lined box & dumped in a deep-sea trench.
Also note its impossible to 5C from the solo / PG part of Powerplay in this proposal.
(this is because the Solo/PG part of Powerplay is focused on the BGS of each Control System, providing all the haulage merits without which nothing can be hauled in Open, plus providing modifiers to make the activities in Open more effective.)
Pledging / Unpledging
You can unpledge at any time. You must wait 7 BGS ticks before you can repledge again to any power, and you start with a neutral trust value of 1. This gives new pledges plenty of scope to advance (and make mistakes) but not high enough to be abused by 5C agents.
Cumulative result : Heavy Overkill.
The other aspect that tackles 5C from 'the other end' is buffing the standard means of attack. This serves to reduce the incentive to 5C passively, simply by making normal attacks more potent. These are again from the Flash Topic (source linked earlier)
"Guaranteed undermine if 100% more than fortification
• A control system that is undermined by 100% more than the fortification value will be undermined even if the fortification trigger has been successfully met
Reasoning: We feel that Powerplay rules tend towards stagnation and status quo, which is not something we intended. Despite all the effort in the world, a power that fortifies enough, against values set by the game rather than in opposition to attack, can remain safe. This change allows sheer force of effort (or numbers) to guarantee systems end up being undermined, making deficit more likely. And to stop this happening, a power must directly compete against its enemies.
Overhead removal and slight increase to distance cost modifier
• Overhead upkeep costs are removed making a system’s base profitability static
• Distance modifier to upkeep is increased to maintain some sense of expansion “gravity”
Reasoning: Overheads are a way to prevent rampant expansion of powers. However, the cost is very high, as they cause an unavoidable amount of uncertainty when calculating CC at the cycle change, as well as just being another level of complexity. We think it would be better to remove them, increase the distance modifier to upkeep a bit, and live with powers that can expand more, as with the other changes in this package we hope that the result will be much more direct attack and dynamism caused by powers fighting each other."
Ultimately, it all ensures that anything someone may be able to do to damage a Power from within, would almost always be time far better spent attacking it directly from without while pledged to an opposing Power. It puts 5C back in the realm of Psi-Ops; extravagant hi-risk efforts to cause confusion & doubt in the ranks of an enemy. But once it has played it's hand & surprise has passed it holds little ability to cause further damage itself. & that is the traditional role of 5C where it has appeared in conflicts historically.
So that's alright then.