I addressed all of your talking points, kiddo!
tl;dr: The Scions as an organization no longer exist, the PC is going to Tural as a freelance mercenary, the contest not only allows but encourages it, Wuk Lamat has shown no ill intent, and Erenville has nothing bad to say about her (even if her boorish manners exasperate him).
We're not a representative of the Eorzean government; we are,
at best, a mid-level Grand Company officer acting without orders, and the story is framed very much as us acting in the capacity of a freelance mercenary. The "colonizer" argument makes zero sense; we aren't going there to prepare Tural for colonization or install a puppet ruler, but to support a rightful claimant to the throne who asked us to help her. We have no clue what her policies are, but given Wuk Lamat's exuberant and outgoing personality and condemnation of warmongering I have a
very hard time believing she would be a bad choice, inexperience with ruling notwithstanding.
As a freelance mercenary, the PC is free to support (or not support) any claimant to the throne they choose. Furthermore, we have no idea what this contest actually entails, and however powerful the PC may be their martial might isn't likely to be enough to win right out; if that were the case there wouldn't be much of a story.
I... don't know how or why you think the PC acting in the capacity of a freelance mercenary constitutes colonization. I'm genuinely confused. The rest is just paranoia.