[Fate]

The research difference would be simple to maintain. Just make a different research unit for each side with more or less research.

A more difficult consideration is the cap-only-ness. For some nations this is not a problem, but for nations with lots of cap-only recruits you are still forced to decide between research and deploying units, ony this time you have a unit that can ONLY research vs a unit that can ONLY fight. I think it would unfairly disadvantage them.

I would suggest editing it in as an auto-summon or a summon-allies.

I encourage you to look at modding. Making such a research summon (or adding it as an ability to every pretender) shouldn't be that hard. The hard part is going through the DB and giving an RP malus to all the mages out there (I suggest getting EDI's excellent DB for this).