The post I was planning to do was getting much to lengthy, so I decided instead to post the link to an interesting video. The vid should back up my point better than I could do with explanations. It's a vid of a huttball match.
(Please note that I don't know any person involved with this video, but I think that the person, who made it, is a great player. I learned one or the other trick from his vids.)
The point I am trying to make is that, when team A scores and team B controls mid, team B has a very high chance of making a counterscore. The separatists have a player who can stay at mid (meaning that he doesn't move beyond the acid pools) and still assist defending/attacking, namely Durge. So the separatists barely lose any defensive power (except near the goalline) while controlling mid, while the rebels would lose an important player in the offense/defense unless they send R2 to mid.
Not related to the vid:
The arguments for R2's combat strength brought up do not convince me. He doesn't have that many tools that can be used in open combat (It is new to me that he has a smoke screen. In episode 5 he created one using the gas ventils on Bespin. It's not something he can do anywhere.). And I still claim that the separatists can spare two commando droids to hunt him down. Any of the 'players with names' on the separatists side can quickly defeat the alliance forces, so the two missing commando droids will make up for the lack of additional firepower by keeping R2 away from mid.
i actually agree with this but The issue I see is that I dont see Durge staying in the middle alone The rebels dont need their entire team to be able to make it to the end zone to score (again see my analyzation on possible score potential) also again with the commando droids gone that is 2 less people the rebels have to kill both of which are going after a non combatant that is not neccisary for the rebels to win only makes it more likely by sending 2 droids after them you are just lowering the seps combat strength without truely hurting the rebels at all. Once durge is incapacistated and placed onto a fire pit R2 can keep it on and he can be incapcitated indeffinately this would not be difficult for any one on the rebel team to do. Even Rohm Kota who was my initial pick along with the rebel forces to try and stay in the middle as much as possible. And finally if they get a counter score it will be just as easy for the rebels to get their own counter score by having Luke and Galen return to the middle again assuming the person with the ball isnt stopped by R2's never ending flame vents. I know you think R2 is useless but you send droids after him and thats all he has to do keep 2 droids occupied he has shown time and time again to be crafty. Also how likely do you truely think the seps will send anything to handle R2 they will see him as largly not a threat something the both the empire and the seps have shown they see him on multiple occassions. He has gotten to many people out of to many bad situations to many times to discount him even if we send droids after him you just weakened the battle strength of the seps and made it even more likely the rebels will score, and keep hold of the center.
List of things R2 has
Rocket booster Cable gun Oil injector
Claw arm Fusion cutter holorecorder
internal comlink Periscope Electric Pike
Propeler Hidden lightsaber holder Fire extiguisher/smoke screen
small saw Air cannon Crashmat
Lariat Sub-mode Umbrella
Flee remover Droid deactivator Computer interface arm
Charge arm (electric shock) Scanners Hose
And thats really about it so ya he does have a smoke screen its his fire extiguisher that he uses as one.
Ultimately I agree with you but you have mixed up the teams. Rebels are team B they dont need their entire team to move the ball only the ball carrier and MAYBE 1 other person depending on who is giving chase if Luke has the ball it requires the 4 commando droids to assist in bringing him down with out that he requires no protection meaning the entire rebel team other then him can hold middle and since you already have 2 droids after R2 this isnt happening. If Galen has the ball it requires Dooku and ventress working together to take him down. (if we are to assume that Durge remains in the middle at all times) but dooku cant keep pace and ventress is likely dead by the time dooku catches up again meaning the droids or durge are needed. You are spreading the team to thin by occupying 2 droids in the search and destroy mission on R2 and by occupying durge to hold the middle you are allowing the rebel ball carrier to pretty much move solo thus allowing the rest of the team to hold the middle. And with the droids haveing only one goal kill R2 those 2 Droids are the most likely to be caught in a special forces trap or gunned down from a better position a squad of 4 is always more efficient and more effective then a squad of 2. The rebels dont have to move as a whole to get the ball scored and I dont see them giving up mid. In the example you give you have to teams mixed up. Team A who might get a score at the sacrifice of the middle is the seps Team B is the rebels that will control mid and get a score while still controling it. 1 person does not hold middle a team does but 1 person can move the ball.