This is something that's been brought up in the more general channels a few times but people have pointed out that OoC is very different between each version. I think given the major version differences and the comments along the lines of "almost getting an entirely new game each release" it would maybe be best to make those previous major versions actually available in some way to those who've purchased.
With how development has been that's basically getting a few extra games if you're willing to backtrack, and would help justify buying it on steam over the free itch version.