This is an interesting question. I think what Dan proposes in this post assumes that the supply would inflate indefinitely, but I wonder if we could cap this as well.
This may involve some questions posted here Why Smart Contracts are NOT feasible on Plasma as in order to cap the total supply we would need the layer2 contracts to be able to track a total supply number in a decentralized way. This is difficult because of the ownership of that supply count and what happens to it upon exit.
I’ll put some more thought into this and reply if I come to anything interesting.