You don't want to monkey with the frame rate for archival, though. Assuming that your 35mm film is 24fps, you want digital files that are 480p24 or 1080p24. If you also want copies in 480i60 or other p60, i50 or p50 formats, for widest compatibility with televisions as opposed to PCs, then generate those from a 24fps digital master. That Wikipedia article calls that "a scanning system rather than just a telecine system", but I suspect terminology may vary.

One problem you'd have with scanning each frame yourself on a slide scanner (apart from the unbelievable tedium, of course) is getting consistency of registration.

Peter