So, I took my first shot at doing something that is truly MS as opposed to prepaid/regular spending.

I went to CVS to buy a VGC in San Jose earlier today - I was told this was cash only, no credit or debit cards allowed. The specific store was at 3074 Story Rd. I have no qualms about reporting something that's already dead.

So, I did not get to the liquidation part. that would be a nice problem to have !
I think even if the post office denies a money order purchase with a VGC, at many other stores, you could buy something with a VGC and the PIN, and then return the item and be refunded in cash. I won't name names so as to not kill this for anyone, but I think this would work. Obviously not scalable if you are trying to MS tens of thousands of dollars, but you could probably liquidate a few hundred dollars every day easily this way if you just have a signup bonus spending requirement to meet.