I don't have a problem with carryover. It has become an issue lately due to 4.a.2.b and large differences in credit hours between fleets/seats. I don't think 4.a.2.b will be around in it's current form when we sign our next contract.
I am strongly AGAINST a cap system. I previously worked for a legacy airline with a cap. One of the things I like about FDX is that you can almost work seasonally. If you like skiing, you can almost take the winter off. If you have kids that play a sport (football?), you can take the fall off. You get the point. You can work a little harder during other parts of the year to make up for periods of time when you want to do other things. If you can get vacation during these periods, that helps with a little cash flow.
I drop a lot of trips and have a large make up bank (almost 900 hours). I don't think I will ever come close to making it up, but I should be able to if I want.
I don't have a problem with carryover, but if it went away, I wouldn't really care. I wouldn't vote for any contract that has a monthly cap.