one of my friends used to play this way. stay at net, in middle, with his partner covering baseline.
i was always too proud to go down the line and would hit straight at him with pace, or try to be clever with a low clearance passing shot... Hitting at him with pace worked for a bit (knocking his stick back a few times), until he realised that he is bigger than a tennis ball and put some weight behind his volleys.. the 2nd strategy, passing shots were good sometimes, but lower percentage... going down teh line was great though. made him lunge out of position, gave us winners a few times and made him less comfortable to stay planted in the middel of the net.
Also, get to the net (or have your partner be at the net also). It will cut off a lot of the angles your opponent can use to hurt you. will be harder for him to win on his volleys.
i rarely play doubles, but this is my limited experience playing such players.
Disclaimer: I'm NOT a coach...
Real tennis: https://www.youtube.com/watch?v=yDqnkLJ9BtM