Not just them. The PoDD cast, Sariel/Konngara, Meira, the dream sisters, and the Makai residents from MS are all god-tier.
But damn is it hard being a PC98fag in these days. Latest PC98hu to be reintroduced in the Windows era was Yuuka 13 years ago, and despite the increasing prevalence of Makai, Hell, and even the Dream World, the only hint we've gotten to the existences of any of the old denizens is some of Hijiri's spell patterns resembling Shinki's. Mima's existence got a few throwaway lines of dialogue in CoLA, but she's probably one of the least likely to appear again.
A lot of the PC98 cast members don't even have counterparts in the Windows fandom. Kotohime is vaguely like Kaguya, sure, but what about Rikako (a magician more interested in science than arcana) or Meira (a human ronin with an apparent grudge against the Hakurei Shrine)? But short of a miracle happening or ZUN getting a spike of nostalgia we'll probably be lucky if we get another reference in the next 5 years, or a returning character in the next 10.