At my previous employer (a manufacturer of custom built trailers) we had a saying "you get it the way you make it"
So anything is possible, but is it worth your time ? And is it worth the reduced capacity of your loader ?
4 in 1 buckets are heavy as they get no support from the back. Therefor they have a hollow double floor, and a double cutting edge. (one on the dozer backpart as well)
If you look at small utility loaders, the 4 in 1 bucket is allways 20% smaller than the conventional, because the empty weight reduces the capacity of the machine. With a front loader, i'd like to travel light, as its already a light duty machine...
In Holland you dont see 4 in 1 buckets at all, my brothers 5 ton Liebherr loader has one, because it was a used import from Germany. But the floor is crooked and the thing is HEAVY ! though not much bigger than my frontloader bucket.
If you want to grab stuff, i'd leave the integrity in your bucket (not cut it up and then weld several 100's kg of steel into it to get the strength back) and just put a clamp on top:
http://www.hekamp.nl/customer_data/upload/files/KB_M_SERIE_FLDR_PRL_2011_V1_1.pdf
http://www.everythingattachments.com/FFC-Round-bucket-with-optional-hay-grapple-p/ffc-hay-buckets.htm
These are just some examples.
Dont know why you want that 4 in 1, to grab boulders, brush, ?? I think of making a brush grab on top of my bucket, but it has to be detachable so it doesnt limit my lift capacity when scooping loose fill...