Frank your Majesty said:
There should either be a plot device, that allows for only a certain number of alternate timelines (which could be hard to introduce without logical errors)
I think it's relatively easy to make a finite SW Multiverse -- that's what I've done for my own personal canon, limiting the multiverse to 1000000+ universes only. You've just got to take care not to violate the first law of thermodynamics when working with the idea.