The map needs to have very little to no dead/unused space. trade_portal and trade_portal2's major flaws lie in the sheer size of the map and how unused and empty a lot of the areas are. A main, centralized hub area to serve general purposes such as pvp, taunting, and spycrab. Or designate spycrab to its own room.
A good example to look at is the original trade_plaza. Trade_plaza has 2 spawns and a decent size main hub area for players to pvp, taunt, and shenanigans.