Because the game is coming out next year, i figured it would be best to request this feature now. Combos, based off the initial gameplay trailer, involve your partner tag canceling. However deep tag canceled combos will get may change during development, but so far it looks like the partner gets to chain for a small period of time.
Pair play is a feature that allows four players to fight against each other. Two per team. I think this would be a fun option because it encourages teamwork.