I think many of them could just be given a few lines of what happened to them somewhere along the way. Sort of like an epilogue for those characters. In some fashion, the MCs may learn what directions their lives went (or ended).
However, then there are those minor characters that had more substance (including character or scene CGs) that may have more of a lasting impact upon the MCs, Bloodmeen, or the world itself. Take, for instance, Ygriss (which unless I'm mistaken doesn't have a continuing or concluding arc for her)...
She is randomly encountered on a mountain hex, but has her own event chain. Depending on how that goes, Ygriss may end up declaring herself as one of Rowan's
wives! Think about how that may go when she finally shows up at Bloodmeen to stand by Rowan's side as his loyal sword and spear. This would be quite an ongoing development! If nothing else, Alexia may have a few interesting thoughts on the matter (or at least, a few choice words) on having a monstrous sister-wife...
Y'know, that's just one example. Doesn't have to be all-inclusive for everyone that the MCs encountered (whether by Rowan or Alexia, or even by others). A few lines stating what happened to them would be fine for the
minor, minor characters; and maybe something with a little more meat for the
major, minor characters.