up for jump is the norm on the amiga, no wonder why you're staying on it
the only arcade game that had up for jump that I remember is Green Beret aka Rush'N'Attack, probably because there were already 2 buttons taken for weapons and 80's arcade cabinets rarely had more than 2 buttons beside the superb joystick. Damn I loved those iron-bar + black handle joysticks.
I completed Chaos Engine (again, after 25+ years) with a joypad a few months ago, so I guess diagonals are not that bad with joypads, but with my wico it seemed easier