In my thought, locking up the coin price in a fixed price will be the same as killing that coins, many people will be leaving that coin behind, because they can't trade that coins to generate profit from that respected coins. It will surely able to be used as a payment tool only.
Using it as payment tool already is more than enough to keep the coin going, although locking it completely without having a little room to move between prices will make investors or traders loose interest but we also have large number of companies too that could make it continue to function which I know that it will be absolutely impossible to lock the price because it doesnt depend on a controlled market system.
But, we have to start having it at the back of our mind that a time will come that the price action of BTC will almost near that of a stable coin, in future, once it has gain the attention of large number of the population and the adopt it, the market will become very less volatile for investor to make any short term or long-term gain, because then, the price would have been too high and very difficult to see it manipulated and by then, will be more useful to Traders, Holdlers for store of value and companies using it for payment service.