You cant give units to championonly players at all - If anything, it allows for a little bit of autonomy at the great cost of being able to capture and engineer. It took me over an hour of completely ignoring my team (who were busy doing spirethings) to get an engineer.
Additionally, ion cannons are still really annoying for engineers..
Alternatively, I could point out that in a multiplayer game, it would be more feasible to have one of the heros in a neinzul ship for the repair field.