Velbon seem to use 1/4" fastening system, so this shouldn't be an issue.
I suppose it may be questionable as to the actual benefit of doing so tho.

Quick price reference checks:

Manfrotto will set you back approx $150 online(not including postage)
Feisol: CB-40 is approx $140 plus freight, CB-50 is approx $160 plus.

Ball diameter makes a huge difference to the operation of a ballhead, and in general you want it to be as large as you can justify.
But at the same time you don't want overkill of the head, relative to the tripod legs themselves either.

So if you have plans to update the legs to more sturdy forms, then consider a larger ballhead to begin with too.