If you're interested in discussing this topic further, I suggest you join the Gen 1-3 Pokemon Speedrunning discord. Most people in the community do not check these forums. In my opinion this would make a cool category, but designing a ruleset that doesn't seem arbitrary might be challenging (f.e. what to do with Sevii). There was some discussion in Discord on this topic when FRLG ACE was discovered.
You can force the Moon Stones and the Cerulean Cave Fossils to respawn by using the date change trick shown here
Note that the Moon Stones are not guaranteed to respawn with this method, but it shouldn't take many tries. There is also one more Moon Stone in Copycat's house in Saffron City. Generally it's more consistent to do the respawn trick than catching Clefable. (This last part might be slightly outdated considering the newfound knowledge on the catch formula)
There is a separate Category Extension for that! https://www.speedrun.com/pkmnletsgoext#Solo_Diploma