I use the 8bitdo

In theory, having a whole new button would be nice. But understand that games are specifically designed around the 18+1 button setup and there is rarely a need for a 19th and a 20th. And if I am going full steam craziness: I tend to prefer modal mappings at that point anyway.

I could see something like a flight sim or an elite game benefiting from ALL THE BUTTONS but… at that point I want the HOTAS form factor. Or we are talking something like the x series where everyone knows the game is meant to be m+kb but we still try to make it work.