Here is how i have been mapping my gamecube controller:
a-attack
b- special
x- grab (no need for 2 jump buttons, z is awkward to press)
y- jump
z- grab
c-stick- smash( i use for aerials as well, atk with c-stick and move with analog)
R- sheild
L- grab( i was thinking of trying this , to make charged smashes easier i could do L + joystick instead of timing it with A or Z. COuld also make doin IC up smash from grab easier)
dpad- grab,atk and smash(unless you are going for taunt gimps they are useless, with a setup like this you can spam more buttons to get out of grabs , yoshi egg, lucas freeze, and other things quicker)