So long as the typical cost of ale legs hovers around 20gp, I can't imagine limiting the gold adventurers carry being an issue. Tax collection is a regular and scaling drain. A recent item improvement cost 75 gold and I've had it as high as 200. A six hour study in the academy costs 24 gold and is as good as throwing it down the toilet. Considering the risk to commoners (of being arrested and their money taken away at any time) I can't see any reason at all to deprive them of their monies.
Rather, give them.something to spend it on! Make guild houses "expandable" by adventurers in the same way temples can be by priests, would be one suggestion. Building and stocking their own home base cabin or homestead would be another.
