One of my friends had chronic arm/shoulder issues and spent hours and hours practicing left-handed serves, left-handed forehands and left-handed backhands. His arm/shoulder eventually got better so that he can play normally now but it was pretty painful on the other side playing against someone trying to go to the other arm.
Yes, it's easy to say but it takes a ton of dedication and work to get your game up to 4.5 with the other hand and your 4.5 friends won't really want to play against you while you're going through that either.
If I lost my right arm, I suppose that I would try the left but I think that it would take a few years to get near where I play on the right.
4 x IG Prestige MP, 70 cm, 376 grams, 386 SW, ALU Power @50