Don't forget the fact that these 10 accounts are controlled by a single entity (RS). The coins that back them are only "unspendable" for the moment, that could change with any release of new code. In fact, there is no way the peasant nodes of Solidcoin can enforce any rules on the control nodes or the block chain.
Worse, it's actually the other way around - until new code is released, the ~12 million coins in those accounts are not in fact "unspendable" at all. The current trusted nodes should reject any attempts to spend them, but RS or anyone else that gets control of those 10 accounts can set up their own trusted nodes that will approve this and the rest of the nodes should go along with it.Edit:
Of course even once this is changed it can be changed back again in a future release.
You are assuming the control nodes run the public client. I doubt any code changes need to be made at all.