Similar to how gambits worked in FFXII, where you could customize the behavior of your team, is it possible to do something similar in XC2?.
You cannot customize your AI - but you can strongly influence it.
The AI will start out on their main blade in combat, and build up their special attack level. Depending on the first blade art done, you'll start a combo (see here for the combo list). So, if you start with Pyra and start a Fire blade combo, the AI will choose either fire or water for their next blade. Knowing this, you can allocate your blades accordingly across the 10 possible blades in your party.
If you do not have a blade combo, your fellow drivers will attempt to finish your Driver combo (Break -> Topple -> Launch -> Smash). So, Tora will switch between Poppis to do it. Zeke will switch to Pandoria to do Launch, etc.
With all this knowledge, you can get a very good grip on how your party performs in combat.
You can only chose the main role of the units : Tank,heal or Dps by linking they with the correct blades. But you can't ask an unit to goes against his role (asking an heal to be aggressive, or a dps to not attack).