It doesn't require any effort but... you want it to be in one button so that you...? What? If it doesn't require effort, it sounds like it's already easy enough. You can't play both sides here.
I play on PS5 and can tell you that controller players have no trouble with how it is currently. I'm not sure where you're getting the 8 abilities from, but starting out you have 16 and can add 16 more on screen with an additional 16 through holding in both triggers. Paladin and Samurai were really the only "rough" jobs in Shb (haven't checked them out in EW yet) requiring some abilities on the "hidden" hot bars. Controller users shouldn't be who you're fighting for this for.
