All good suggestions, I think. For Dr. Bashir, the augment angle would be a link with Dal. Garak is always interesting, and the actor may be available if there is no make-up involved (which happens to be fine for an animated series). And Ezri Dax is a counselor, could be useful both for Dal's group and for Gwyn. And none of them were featured in Picard.
It has to be Worf. Dorn must be in everything. The TNG fans will be happy with S2 has me thinking it will be a TNG/DS9 character: Worf, O'Brien, Keiko (sp).
Or maybe Ro? Q? Guinan?