[Autumn]

The way to go might be bonuses via the Monk Method, where in Spirituality currently doubles when mono-classed, though I think that part is kinda weak currently, there could be some cool bonuses like...Arbalests having -1 duration on being locked out of cannon skills, Kensei's 'katana master' being doubled or tripled, Black Knights always having the black wind active. Etc.

I think a good example with kenseis having like, tripled katana master, that'd set their Sakki/Touki/Kenki/Yomidori all at lvl 30, making them feel like masters of their art.