- I think that removing the event troops entirely or setting a maximum value would be better than just lowering the scaling as lowering the scaling itself still will run into problems at some point as a realm grows (at 100k realm levies after the revolt you'd have 10-20k troops spawn somewhere that may or may not make sense, such as Malta (where they might get stuck if that vassal isn't too powerful), Finnmark (low supply and likely low population), or deep in the steppes (good luck bringing them where it counts if the main realm isn't in the steppes)). Regardless of the method chosen, it might be a good idea to also increase the ultimatum threshold somewhat to make the AI wait until it has more of a numerical advantage before trying to press the issue to help it a bit.
- I personally feel that the Independence faction should be joinable by vassals that might want independence (and that could have joined the faction before the war) as it would make things interesting if you have a big empire and more and more parts of it seek to secede unless you decisively stamp out the revolt very quickly or take steps to ensure that the other vassals remain happy with you (e.g. a large HRE containing France, Italy, Poland, and Hungary in addition to its 1066 de jure might risk the French and Italian vassals joining the revolt if the Polish-Hungarian independence war drags on and the Kaiser is unloved). Claimants might make sense to restrict, as the AI's long-term planning isn't terribly good (in the example with the claimant brother supporting his cousin, the AI would not necessarily carry out the "Backstab my cousin" stage of the plan, or might backstab the cousin by joining the war to restore its brother).
- I like the idea of some vassals (or the ruler himself, if unlucky) losing some land during a revolt, and the fact that that generally doesn't happen at the moment is one of the reasons I'm not a big fan of the revolt titles. However, the old system sometimes went too far in the other direction, as you could declare a number of holy wars on multiple revolters on the same day and then take multiple duchies with relative ease during the revolt (particularly as the revolt leader was unable to surrender if any revolter's land was occupied), which is why I think that it should be restricted in some manner. It could be through mutual alliances, inability to declare war on someone if you are fighting someone with the same pre-war liege, or something else, but the exploitability of declaring on multiple revolters at once was significant. Sure, if the civil war drags on you should be able to make multiple land grabs in the area, but if it is possible to do so at once it would mean that players with the old faction system would have a massive advantage with the land they could grab during a civil war over those with revolt titles.
A couple more problems I have noticed that might need to be looked at if the old system was added back:
- Revolting viceroys currently turn their titles into normal titles with the old system modded in. It makes some sense if it happens upon victory as you could write that off as the faction members making that part of the peace treaty, but it happens upon war declaration and gives the pre-war liege claims on the titles. This results in the liege wanting to revoke the titles (tyranny free as he has claims) even if he loses the war (with the other rebels not caring at all until it is their turn) and sometimes results in the pre-war liege forgetting to revoke duchies/kingdoms (possibly due to not wanting to have too many duchies), meaning the traitorous ex-viceroys' heirs inherit the titles. I suspect that the best way to handle that would be to remove the liege's claims on the revolters if they force through their demands and programming the AI so that it revokes the titles more quickly if it wins (though it should of course avoid getting too far above the duchy limit for a long time).
- Aside from the leader, revolters who die currently have their heir instantly re-join the pre-war liege's realm. It is a bit of a problem if a revolt consisting of old vassals fades out because they die natural deaths, and with the viceroyalty issue it could have the suddenly loyal vassal lose his titles anyway after the war as the liege sees a claim and wants it. Some kind of coding to fix this (or to give the heir a choice about either continuing to rebel or joining the loyalists) should probably be implemented to handle the issue (I don't think it was a problem back before RoI, but it has been a while). The suggested ability to join ongoing civil wars might go some way towards solving this issue.
I don't think that any of these issues are insurmountable, but it might be a good idea for the devs to look at them if they add a switch as it might cause some unintended consequences otherwise.