House Manwoody might be good?
I'd say we don't need Manwoody because unlike the other Dornish Mountain houses, they've got a black banner, rather than yellow (Yronwood, Wyl, Blackmont, Toland, Caron) and so will be pretty identifiable among their neighbours with a black banner flying from their standards. I'll fly Vyrwel/Black banners + Reach banners on the closer Darkdell towers so that its obvious its a Reach castle and there shouldn't be an overlap where you can pass by a Reach tower before a Caron tower when heading north out of the Prince's Pass.
Compared to other Houses nearby, Manwoody isn't really relevant within the story except for background + a little bit of F&B lore. We have no characters of note visit their lands and no real need to use a special banner to distinguish them. So I'd say they're v low priority on the banner list. The Hogg, Wode and Sow's Horn banners are higher up on the list, imo.