The closest thing i came to actual keymapping on a old-skool sampler is a simple one.
make 1 sample with 64 notes in it… slice it… and play it in slice-mode…
here is the trick:
make a sample… a big one with 64 notes in it… there is a but though:
you got 16 triggers… and it is handy (it was for me) if your triggers keep having the same note under it…
an octave is C. C#, D, D#, E, F, F#, G, G#, A, A#, B but those are just 12 notes…
so add a few to get 16 notes… your list will end up something like
A1#, B1, C2. C2#, D2, D2#, E2, F2, F2#, G2, G2#, A2, A2#, B2 , C3 , D3#
thats 16 notes…
A2#, B2, C3. C3#, D3, D3#, E3, F3, F3#, G3, G3#, A3, A3#, B3 , C4 , D4#
thats 32notes
A3#, B3, C4. C4#, D4, D4#, E4, F4, F4#, G4, G4#, A4, A4#, B4 , C5 , D5#
thats 48 notes
A4#, B4, C5. C5#, D5, D5#, E5, F5, F5#, G5, G5#, A5, A5#, B5 , C6 , D6#
and thats 64 notes 
So all you do… is space all these notes out evenly in your daw, with some vst or a synth attached… record it… slice it by 64… and every slice should have 1 note in it.
if you play in slice-mode… you should be able to play it like a keyboard…
and if you switch between slice-pages (u got 4, because you got 64 slices) everytime you go a page up… all keys still keep same note… but one octave up.
and if you go page down… all keys still keep same not… but one octave down.
on top of this… you can still play in chromatic-mode… and play a melody with your melody (it sounds more fun then it is… but still… its possible)… and you can play with the rate button… which is fun… rate64 is normale speed… rate48 is 1 octave down… rate32 is 2octaves down… and rate16is 3octaves down… (well it should)
But keymapping like my mc909 or mv8800 or renoise does… nope… thats not possible…
Enjoy your day…