This can be done (and already is possible afaik) on layer 2 like lightning, so it would not require any hard fork. (A hard fork could also do this, but fuck that)
Discussion
If that's not fixed on the main layer, it could lead to centralization, as only large institutions with significant Bitcoin holdings would afford to transact there. Self-custody would become increasingly expensive, eventually pricing out individuals from paying transaction fees.
Not a real threat today, but conceivable in the distant future.
I agree partially. There are however options to use lightning in self-custody, though that requires a bit more technical knowledge. Hard forks should never happen, except in some unknown emergency. I'm carefully optimistic that there will be plenty of second layer options by the time it would be a problem.