[PvK]

I don't think it's a balance problem, but in some cases it can be a little implausible. If you have a ton of cash reserves, it can make a bunch of troops appear instantly, often with nation-specific equipment/type. And, it can be done even in isolated provinces that don't have a ground route to the main nation. So in some cases, say Ulm summons some black hawks behind enemy lines, and when the enemy comes to reclaim their province, they find a bunch of Ulmish arbalesters and if enough was spent, heavy infantry of Ulm.

The free regeneration seems a little bit artificial/logically-strained compared to the costs of recruiting regular troops of the same type, too. For provinces connected to your homeland, though, it can sort of make sense following the apparent assumption that there are men with national equipment and training floating around but not part of the usable army until paid for. Assuming that, it's sort of like a reserve militia, national guard, or something. Still a little weird that their losses have no effect at all (except maybe the dead body level, and the experience levels of enemies that kill them).

It's not perfect, and a little gamey or illogical in unusual circumstances, but for the most part I think it works out reasonably.

PvK