The portal servers already give you the ability to kick, ban, restart map, and start next map.
The only real things missing is the ability to add more admins, and manage teams. I don't think it would be hard for them to add those features to portal and in-game.
Spectating was always a game design thing; they should consider adding it either way. Screenshots were useless since people used cheats as an overlay, so that isn't missed. Team balance was a plugin, if admins didn't want to move players manually. Theoretically, we already have the ability to team balance by adding it as a script or block program; only problem is the performance implications and the generally bugginess that sometimes happens with rules not triggering or terminating randomly in the middle of a triggered rule.