On the PC I actually use the keyboard to control both characters. In some ways I can simulate 2 player matches by performing a move, and then countering with the other character in the form of rush down, or a punishable special like a teleport punch, or jump in attack.
Also, sometimes I will set up the arcade stick so it controls both characters, but in order to move player 2 I have to hold the block button, or P1 Block + directions and run. Basically what I do is, move P2 by holding block and essentially it just makes them player 2's controls on the fly and player 1 cannot move while blocking.