The main issue I see with this is that there are one of two outcomes, at least as far as I see:
1) The casters can easily acquire their new pouches, with minimal delays.
2) The casters cannot easily acquire their new pouches, facing significant delays, danger, or cost.
If 1, then the rule is pointless. A pittance of coin barely worth noticing. If 2, you're nerfing casters (which is not undeserved) but in a very slipshod and minuscule way. And, most importantly, in a way that feels bad, least to me-but I'd wager that many other players would agree.