I mean... heroes can already pump up their units for free in certain regions, can't we do something on that scale but for pay?
With heroes its random when they can and limited effects. Its also a part of class that has otherwise little benefits but is the only way to be able to die in battle and it can not be reversed so its not like heroes being able to do it is a casual minor thing. As well its been explicitly stated that recruitment in regions other than the capital is not wanted, so suggesting something to circumvent that is obviously not wanted.
I am all for discussion and suggestions, but suggestions that try to circumvent mechanics are not very helpful.