I am sure it will look great when done, if you can be bothered it would make an interesting writeup on how it is done, I have a few brushes that I like the handle but would prefer to change the knot on, just never done it before and scared of damaging it.
I get the principal, remove old know, Dremel or remove the existing glue and stick another in but it is interesting to see that brush with the knot chopped, you are well beyond the point of no return. I think the hardest part would be selecting the knot and setting it to the correct loft.
Nice work, will look forward to the end result.