I consider it more analogous to choosing to fight those Hydras without engineering, and then complaining that they get rewarded the same as those with maxed-G5 mods. I choose Open because I enjoy occasionally testing my evasion skills against other players, and the thrill of successfully doing so is my reward.
Any player can obviously decide to add a challenge of his own to the already existing rules and balance in any game. We are also even free to act foollish on ocassion, both willingly or unwillingly

. Nothing wrong with it. The thrill of it is our reward. This already happens in all modes, Solo, Group or Open.
The bottom line is many games are have rules based on progression obtained thanks to rewards that are generally commensurate with the risks the game environment presents by design, irrespective of how many more challenges each player personally decides to include into those.
And the emphasis is on occasionally. Realistically, there’s less than a one in a hundred chance of ever encountering opposition if I stay away from where the PowerPlay PvPers like to gather when the stars align. A realistic reward to offset my actual risk would amount to a 0.3% bonus.
Well, if the risk of playing in Open was actually so low, then we should not be finding that there is so much contrary opinion to those requesting to make it open only

(I think all modes should be optional either way).
But more serilously though, yeah, in a game as huge as Elite there are indeed areas and content which would naturally carry more risk than others of course. But I think we all can agree that playing in Open carries a certain level of additional risk. The size, or even location, of such a commensurate reward would eventually be, of course, up to FDEV to define and balance as they see fit if they decide to go that way. It may very well be, for example, that FDEV considers to put in place a system where the commensurate rewards in Open apply only to, say, PP2 progress
The game should reward
actual risk, not hypothetical risk. Give me a bonus for running the gauntlet in a PvP hotspot
when PvPers get instanced with me, and then we’ll have some fun.
I personally would also welcome specific PvP missions or scenarios like the ones you suggest, as long as they are appropriately rewarded, commensurate to the risks indeed (i.e. an average NPC conflict zone played in Solo or Group probably would not be as risky as a PvP one). Having said that I suspect some players may complain that they can not access that content if it is somehow of a new kind.
As for hypothetical risks, playing in open carries a very real and tangible risk. Not only because players that want to combat you will generally be much better prepared and more efficient than many of the NPC´s that can attack you, but also precisely because of the powerful fact that they would be ubiquitous and fully out of your control regarding the time and place of the encounter, unlike most NPC activity.
The challenge here is double: First in how to strike the right balance for the reward. Let´s say on average you get destroyed by enemy combat players in, say, 1 out of 3 times that you get to a particular spot for a particular PP2 action. In Solo or Group that would have never happened but here you lost your ship and/or cargo once in every 3 trips more than players in Solo or Group in the same location. The rewards in Open for those times you survived needs to account for that (be it in credits, PP progress or whatever FDEV may eventually decide). And second, how to prevent that the system becomes too exploitable. This second challenge, of a technical nature rather than game design, I suspect, is the main one.