the current system is one of the best IMO, the only better system is the EA MMA choke system. For UFC 4 I'd definitely like to see a more back and forth struggle based system, with opportunities to transition in a variety of ways. I think it's a but late in the game to change it completely for UFC3 but it can certainly be expanded on. one thing I'd like to see is the ability for certain fighters to pull a sweep when you have a sub pretty tight and your opponent may escape, you could go for a sweep...like a kimura sweep or a triangle sweep into mounted triangle position. of course that transition should be able to be blocked and reversed and put you in a compromising SUB position.and definitely we need more factors that determine the amount of gates, and as many have said Maia or any of BJJ guy having back mount should feel be an extremely urgent situation. I also like OPs idea of allowing use of the muscle modifier as well.
that said, it frustrates me to hear that so many people think Subs are useless, because the dev's knee jerk reaction will be to make them easy to pull off which they shouldn't be... subs can be dangerous if you use the current system to its potential. I dont even use the RNC/Trianlge into armbar two gate unless I'm desperate. most of my sub wins are 4
-5 gates,and I've always have more sub wins than decisions since UFC 2. I dont think I'm hot **** or anything I just took the time to get better, and didn't stop going for them because they were difficult. you have to be able to simultaneously react and predict gate escapes AMD set traps
of course if your fighting relaxed guy ,crooks,suspect zero (who is the only guy who's non 2 gate subs scare the **** outta me) or lurch or any of the highest of high level players going for subs is a shot in the dark but against most players even very good ones subs CAN be a threat in the current system
here are some good examples of that vs very high level opponents
Subs with Vitor
https://youtu.be/Tz__l2maohg
Lietes
https://youtu.be/SAqnzZkrwo0
Olivera
https://youtu.be/g7k2NKyuT-w
https://youtu.be/utMHJUC9nz4
Usman
https://youtu.be/WbPQoQoFbT0
Serra
https://youtu.be/xwo8M6rxlpk
Compilation of good subs against various level opponents
https://youtu.be/iarRrMi9HYc
Matt Hughes - not a high level opponent but pretty good sub on a decent opponent
https://youtu.be/oYl9GtrJKp0
if you notice, barely any of these subs are reliant on having a stamina advantage. and this is not showing off in any way. I'm pretty good but inconsistent and lose plenty of fights lol even ones I really shouldn't. but I'm just sticking up for this sub system because i think it's pretty good , I just think people dont take the time to really learn what works and get discouraged quickly. you can't practice in the lab the only way to really get good is going for subs against good competition in ranked and keep trying until you get good predicting and reacting on the fly to the many different methods people use to escape.
sorry for the essay (im actually annoyed myself that's it's such a long damn post) but hopefully a few will be inspired to keep trying with the subs because they are effective ,even simply for scoring points and doing damage.