That's possible in theory, but I think there's been exactly one CG since the new storyline started in September where several hours of effort wouldn't get you well beyond "top 75%", and that was a very unusual case. (And I think it's fine for there to be the occasional unusual CG like that - we want Frontier to experiment with the format because that's where improvements come from)
Looking at the recent CGs:
- Trade: 4000t delivered almost always gets you into top 50%. That's doable in just over an hour if you have a T-9 ... certainly doable in four hours with a T-7.
- Bounty Hunting: 20 million credits would get you into the top 50%. Just basic RES hunting (not even HazRES) should get you that in less than four hours.
- Combat Zone: 7.5 million credits of bonds. Again, should be straightforward to get in four hours if you can do CZs at all.
- The other CG types are a bit rarer, but again, four hours of reasonably consistent effort - in a suitable but nowhere near top-class ship - will get you top 50% in them.
I take your point that
in theory you could throw ten or twenty hours in and still end up in the top 100% no better off than if you'd just handed in one item and moved on ... but in practice that's not how they end up working. In general, an hour's decent effort will get you "top 75%" ... four hours will get you "top 50%" ... it's the top 25% and above you really have to start putting time into (and where the amount of time needed starts to vary a lot more)
Also, of course, most CG types - this week's being a rare exception - also directly pay you for whatever activity you're doing, and that payout is generally at least as valuable as the tier bonus anyway.
Every exclusive module so far has been handed out at 75% with the sole exception of the Enzyme Missiles for the losing side in the NMLA CG (and that experiment I'd be surprised if they repeated in that form). And 75% is in practice fairly low effort to get no matter what the CG.
Rewards for tiers above 75% have either been cosmetic or non-exclusive or both.
....and with two of the CG modules then being released through Tech Brokers, even then the rest of the rewards are probably only temporary exclusives too.
I would agree with you that handing out exclusive module rewards at the 25% tier would be a mistake and counterproductive: Frontier also agrees with you on that (the one time they advertised a CG as top 25% for module rewards, they decided to actually give them to the top 75% anyway, presumably because it didn't really work out)
Something I've also found on CGs I've been involved in is that being dropped down a grade isn't necessarily a bad thing - the last CG I did, when I stopped handing in, I was in top 25%. By the time the CG ended I was (entirely as I expected) down to top 50% ... but in the meantime the overall CG progress had risen a couple of tiers, so my payout bonus was higher than the one I had when I stopped working on it myself.
