1.)  The 144,000 bitcoin is trackable.  Users will be less likely to panic into a side chain they know is heavily invested in by the gov.  Besides, I don't think 144,000 bitcoin is enough to cause a panic.  A few of the top alts have market caps near or above this and I don't see a panic into those coins, of course those alts are not pegged so there is risk in moving.
2.)  Any buying of side chain coin and/or buying of processing power to attempt a 51% attack on the main chain will invalidate the risk-free put, even if printed fiat is used. 
3.)  Arbitrage of an asset pegged at the protocol level will probably be effective, especially if multiple exchanges are involved. 

Of course the only thing protecting bitcoin from losing its MC status is the block subsidy, so there is real risk that over time bitcoin could cease to be the main chain.