I have put new limbs on a one piece riser, but it was on the same form as built the first time. Just sawed the limbs off , then sawed thru the lams, staying out of glass and riser and sanded the riser back to where it was before gluing up the first time. Then started on new bow with old riser.
PITA tho!
You will most likely have a different bow bow profile than almost anybody else so a new form would have to be built for it , if you can get the riser extracted from the old bow.
Heck, I had a new style bow first try come in way heavy so I sawed the whole bow end to end, figuring it took about .035" out of the stack. Glued it back together and it worked ..... for awhile. I didn't have enough clamps to get a good job on it and it folded.
And before ya ask, I'd already redone the form to a new shape...