How do you headcannon cross-faction ship captains?

My captains have always been "lore-friendly" in terms of my klinks only fly klink ships, Rommies fly Rommie, and JemHadar are limited to the vanguard ships. I'll fly to farm starship traits but otherwise I keep them cannon.

But I have so many FED ships that I own and want to fly, and the stories just mostly make sense from a FED point of view these days. I feel like I need to create more FED toons or somehow justify a Jem'Hadar or Romulan in command of a starship.

Most people don't care about this head-cannon stuff, but for those who do, how do you justify it to make it make sense to fly around in cross faction ships?