Carrier loses weapons when he picks up flag. Weapons consist of Rocket Launcher (gain speed) and Rail Gun (shoot people for -speed based on distance from target, so 1000u away would make them lose 100? 500? ups, but 100u away would lose 10? 50? ups), and melee to force a flag drop, with no speed loss.
Chasers have both weapons, RL does nothing to other players, RG also speeds up team-mates with a lessened effect (half speed gain or something).
There was a Q3 mod that had classes, one of them could spawn a launcher/jump-pad for a certain amount of points. Maybe the FC can spend points to do something like this, a small portal-type object that speeds up team-mates and slow down enemies.
Flag caps are not the points one would spend; capturing a flag gives the team 1 point, but the player who capped got 100 points, assists (dropped flag for someone else, forced enemy to drop flag, returned flag, etc.) give 25, hitting an enemy gives 10, and maybe there can be randomly spawning point pickups for 5 points.
This sounds kinda fun. As someone said earlier, there's no way to know how something like this would work out without simply doing it.
In order to test much easier, it would be nice to create some sort of modular back-end for rulesets, where every type of variable can be changed easily from each user. I dunno how programming works, but Excessive Dawn has custom ruleset cfgs, which are pretty nice, even though I've never used them.