Originally posted by jonnin:

possibly as simple as changing 'iscontainer' to true and 'num_slots' to 20 or whatever.

Was thinking at something like that, yes: all chests' mechanics are already in place, the same as, if they want, the "secure chest" (personal one), slots and so on. Don't know if it needs code, to allow an item only (coins) or it's just to configure the "master object" to accept them only, but it seems nearly-to-zero effort to me too.