Oh, no way was I neglecting Umber, it's more that something sparked in my brain that there would be a nice fit with Capitar, since warhorses are already their "thing" and they're in dire need of more interesting abilities (whereas Umber were already interesting & powerful). But I would never advocate bringing back one without the other.
I really like the idea of Umber getting a lot of beasts, especially the boars, and they're in need of some new identity now that Serpent's Pact is gone - I don't particularly like them having Master Scouts since it's such a core part of Tarth's identity, would much rather they had some unique beast/mount related abilities. The Greenskins in Heavenfall's mod have some neat abilities along these lines - warboar mounts and special abilities using their bond with them - maybe Stadock could borrow some ideas from there.