Has it been discussed before to allow nobles to partially pay their units?
Requested, discussed, and rejected.
Would allow for longer campaigns in enemy territory or make it more feasible to have a campaign in an enemy territory on the other side of the continent, much like a crusade no?
This is not something that has historically been encouraged. If you want to fight wars, it's much better to fight closer to home. For one thing, you get a lot less of "march for a week and a half, fight a battle, march back for a week and a half." (Or maybe not even fight a battle, but sit there for three days staring across a border at an enemy army you can't beat.)
Fighting close to home is a
lot more fun, take it from me.
