[Miki1988]

Well, they obviously had the original blueprints for the suits and all there was to do was to actually re-make them. I doubt they would be able to do as many suits as they did if they didn't already have the original blueprints along with instructions and other additional notes needed to re-make them. For them (Toei), it wasn't too hard to re-create the suits, since they already made them once back when their original seasons/shows were being produced so they already knew exactly how to do re-create them as well.

And the best thing about this is if the suits eventually become useless they can always re-create them if necessary.

However, for fans and non-fans who would attempt re-creating the suits for themselves - yes, it's a bit tricky for them, I'd say. Plus it takes even longer to re-make just one.