I think the only reason that could exist is simply if one had to get it running with the least amount of money. Any time savings doing it thru the existing drivers is going to come from the fact that someone else has identified the work and connections involved, other wise it probably would take longer to figure out the existing mess from scratch.
I would go all new without any hesitation. The components required have never been as affordable, and in the end, you won't have old technology... where perhaps the age of it could make it fail, making you start all over.
If there is an introductory money savings to reusing anything, reuse just the motors to get started, as they are a simple swap to something newer, better and more powerful once extra cash is available.