If I did lose the use of a hand permanently, I would probably try making a custom map with chording, there's definitely a payoff there.
I'd say it would be worth learning alternative keyboard maps if: A) you work remotely and have a single computer or set of computers you can permanently configure with your preferred layout. B) You're a wordsmith/writer and produce large amounts of textual input as fast as you can type.
I think getting a base touch-typing competency matters far more than optimised layouts, even though the latter can improve comfort/accuracy/speed even further.
In comparison, the text-input methods for smartphones and portable devices need to improve drastically. I find myself getting frustrated whenever I need to input more than a single sentence of text into a smartphone. Using terminal emulators or trying to write technical code/information is a nightmare.