Or they could just not mess with it at all and keep it how it was in D:OS1, which didn't have any issues.
D:OS1 had huge issues. In the classic game, there was no limit whatsoever on how many abilities you had available, which was a balance nightmare (and not that interesting, honestly). The Enhanced Edition limited how much you could KNOW, period, which was just terrible, because you had no flexibility unless you wanted to keep buying new skill books every time you wanted to swap out.
Memory is a good idea to create a middle ground between the two. It just needs tuning to make it less... annoying. As I think has been suggested, having higher levels of the relevant skill reduce the memory footprint would be a good start.
