Personally I would say at this point the relationships between versions are so confused it would seem best to start from scratch.
the 80 tablespaces aren't helping this one bit.
I am really curious what lead to creating that many tablespaces? reminds me of 1990s Oracle databases where disks were small and you used lots of them, and spread your tables and indexes across many different drives/mirrors because the raid at the time had performance bottlenecks.
Well the original architect started out in the 80s with banking databases they just kept that model without revisiting if it works well or not, that might explain it a little bit. But also given the size of our tables we use the physical disks and filesytem advantages to improve speed and performance of the application, but not as often as I would like. We have a pretty big database.