I don't think I could bother, I've never paid for a game... Although I would consider if monthly charge gave the guarantee that steady & major progress is made each month. But for this to happen, fl- would need to treat the mod as a fulltime-job and should thus be paid accordingly. 2$ Will not suffice in achieving that, you'd need at least 10 - 15$ a player with our small playerbase.
Wether it's 2$ or 10$, the fact that players have to pay monthly, regardless of the amount usually causes the biggest decline in playerbase already. Once people are interested & capable of playing monthly, they'd pay any reasonable amount. Let's also not forget though that most -18 year olds would be left out since they don't own a credit card, and last time I checked, we have a significantly large amount of -18 year olds in this mod.
In addition, THQ/Relic will not tolerate anyone making money with a modded version of their game and they would just sue fl-s ass
. That is if the expected decline in players (monthly charge = big decline) in an already small 'potential player pool' (CoH mods are not nearly as popular as other game's mods) doesn't kill the mod to begin with.