I was going to read the whole thread before I replied but I got distracted and then you noticed me before I updated said post. Fufufufu. I'll update this one.
I D E F K. I wanted to make a list of all the possibilities (and did elsewhere) and I just couldn't fully lock it in. The least messy interpretation I've found so far (the one with the fewest assumptions, throwing the fewest wrenches into our knowledge machine, such as "This overlord is still self-identifyng as Solus but he's not." or "Sometimes these entitites can just whip up a physical out of nothingness.") is that Solus was a Legatus and had a kid before being risen to the ranks of the Ascians or that because he still had his original host anatomy there was no affect upon reproductive faculties or if "mortal transmigration" (see Soul Shenanigans) really is a thing, it copies said host anatomy and ... I'm gonna wait for him to explain.
This is true. Travanchet was the name of a random Elezen adopted by the Ascian soldier.
On the other hand, his Ascian puppetmaster was still playing the part.
I've been suspicious that all the blonde hair and blue eyes was just to evoke (from the audience) negative associations of "Ah, they're the racial purity folks." Essentially Garlean Malfoys. Now that this is firmly rooted (especially vis a vis the Optimates) we can see the actual phenotypes, lol.