I think that it is necessary to understand whether the mining work is proportional to the number of transactions in the block chain.
Also the paper should note, I think, that keeping extending the block chain is a desirable side effect of the mining that keeps the ‘bank’s books’.
The coalition stability analysis is from the 1944 von Neumann Morgenstern Game theory book.
What if a ‘government actor’ is a single member cartel?