1. More gibs
We just released a patch which increases the gibs. I still think it can be improved as I think ragdolls are visually confusing. Ideally I want to make a big visual effect when someone dies, so its obvious when its a dead body flying around vs a real person flying around.
Also we just patched to create SG gibs
2. Team colored sleeves
As squeek says, we agree this would be nice. Don't forget you can have a team colored HUD which makes it more obvious which team you're on.
3. Teleporters. Read the FAQ
4. Maps. Most of what you mentioned is already made, look harder!