Anti-lag code is... selective... it can easily be applied to some weapons and not others. The main problem I see is that WFA is *SO* much faster than normal quake gameplay that 500ms leeway will make a huge difference... Enough that you will be pissed when you die in locations that noone should have been able to hit you in.
Another VERY serious consideration is A) Bot usage and B) Weapons balance. Right now the weapons are balanced (even if you don't think they are) to take lag in to effect. If noone had lag, weapons would be WAY more powerful (at least the hitscan ones would be.) That includes the lightning gun, rail/sniper rifle, mega, hyperblaster, etc.
All those weapons would be doing way more damage because you wouldn't have to lead your target to account for lag. Additionally, bots will NEVER miss. Lag actually gives a little bit of bot protection but if the game is "unlagged" bots will never ever miss.
Half the people seem to think its a good idea to use anti-lag code, the other half don't. It wouldn't help Grappling, or anything like that either way.
Static
PS: I don't know what the "50 ms internal quake lag" thing is that the CPMA people have been playing around with. I sent them an e-mail a while ago and they said they don't know if they want to share or not. The type of unlagging I'm referring to here is using the attackers POV when determining weapon hits.