Cool answers, I'll reply randomly.
1) Allow players to have "one kind" of each, so they can switch even if it's more expensive to have weapons of each and buy ammo for them.
Remove one rifle-like weapon and make it a flame thrower. Don't keep client compatibility because it's a lure, in fact I think people won't play the game much without the client, and won't play it much with the client. You knew from the start this kind of mod will be better once 0.6.x is released (God knows when) and it is an use case that can show some features required in 0.6 for modding (just like Tee Shields).
Look at the "Fire" (previously gCTF) and the "TeeSpace" mod for ideas to change the weapons, I find them far more original even if they are overpowered (especially in the Fire mod).
Make one of the "shotgun-like" weapons a repetition gun with extended ammo (let's say 1 ammo = 2 bullets, 10 ammos) that has automatic fire.
Make another of "the shotgun-like" guns a shock gun (that lasts VERY VERY few time and doesn't stop the tee but just prevent him from jumping/hooking/shooting for like 0.3s, he keeps his momentum though). Long range, long cooldown. Maybe?
The sharkbait is imo a bad idea gameplay wise, it might be fun, but what behavior does it encourage besides playing pussy, campers and aimbots?
Also provide the vanilla weapons WITH the same damage value as base reference for all other weapons
That is, don't limit yourself to 3 weapons by genre! You can propose more, but only 1 of a kind (+ pistol + hammer) at a time. This is not the best solution but better than nothing. No switching between real weapons really sucks.
2) I agree with what has been said, keep the weapon after death if you don't make it a pickup game.
3) I continue to say that while some gametypes shouldn't have hearts/shields (survival), some gametypes should.