I suggest the following:

1. Disable physics at least for original map or all buildings.
Because players very often destroy buildings or all map just destroying bottom "layer".
2. Make players drown in water. Because no sense in islands and bridges if may make stairs or tunnel to water and just run across the water to another island.
3. Limit the transfer to another team(For example, like in Counter-Strike).
Because may easy go to another team and teamkilled teammates and destroy enemy buildings.

I hope, with these suggestions, game will be more interest.

-------------------------------
Sorry for my bad English:)

1. no, this is part of the game, and removing it would remove quit a bit of the fun
2. HELL no, im not even gonna bother to give a reason
3. maybe, this could be usefull so one team doesnt get flooded while the other is all alone, but tbh, i love being 1 vs. 10, even if all ten try to get me at once :P

2. Why no? It added more fun in game.

PySpades has (or had as of 0.52) a feature which prevents any original landscape blocks from being broken, but I must say that it sucked.

Drowning in water: No. Just no.

Team-forcing features: Pyspades had this too. I hated it. So did most of the people I played with.