If it's possible, turn off HLStats except for the bonuses given at the end of the round (Goal, Best Shot, Distance). Some people take cube soccer as an opportunity to inflate stats. Going in with that mindset means that person will try to get as many kills as possible instead of trying to score a goal, defend, or anything that involves the cube. Doing this may also attract in some people who take pride in their stats and want to play cube soccer without fear of losing their position.
Next I'd like to address some additional class restrictions. I believe the following classes should join Sniper by being disabled.

This class, like Sniper, encourages the player to go after exclusively players instead of the cube. The only other weapon the Spy has is the Revolver, which doesn't do much to pushing the cube anyway.

Aside from the shotgun, the Pyro's weapons are useless for pushing the cube. The flamethrower simply encourages more player killing instead of anything else.
Spy and Pryo I suggest because these two classes are like Sniper in the case where both don't do much for the cube and just result in the player going off killing players which I don't think is healthy for cube soccer, especially when the server is full. Players that just exclusively kill other players can make the game degenerate into deathmatch with just a few people even caring about the cube at all.

A special case here. While their shotgun and to some extent the pistol can be used to move the cube, it's the sentry gun that causes problems. Specific maps make it easy to lock down an area or camp the spawn and detracts from gameplay in general. While sentries can usually be stopped, the fact that it remains a possibility is also unsettling.
I'll have a few more issues to address later, but I'll let these sit for now.[/quote]
See, now, I disagree to a point. Pushign the cube is the main goal of the game, that is not contested.
However, having Spies and Pyros on the field to disperse the opposing team and let the Scouts and Heavies push up is a vital part of the game. Striking a balance between clearing a path and shootng the cube through it. Snipers are overpowered as they can fire precisely upon the enemy team from relative safety, but Spies and Pyros get blown up as much as anything else on that field.[/quote]
Agree'd. Even though the primary objective is to move the cube you still need to attack the other team. If you can kill members of the other team it can really help to move the cube down the field.
I will agree that snipers would be lame and I think SG's are a bit lame too.