I don't really care more about the IC aspects of the discussion, we could be discussing Kepler and Evilburg for all I care. I just want to point out how redundant it seems to do what you wish. The name issue was perhaps the only thing that did seem sensible for requiring a new realm. The rest seems perfectly possible without a week-long capital TO and several more weeks of creating new-realm delays, depending on how well-oiled the plan is.
Delays such as, are you creating a new duchy for the new realm? Wait another two weeks if you haven't made the duchy yet. Or using an existing duchy to secede asap after taking city? You saved two weeks. Are you going to linger around more weeks and months to get everything perfectly ready for the new realm, but oh wait, now the realm needs to finish a new war before we can form the new realm? Etc.
Fighting to the last is at least engaging to the players. I enjoy the diversity of experiences in realms making the decision to bend the knee for survival and revenge-another-day (or not) or fighting to the glorious end; different realms have different cultures and histories affecting such decisions. I don't fault Barca for choosing to fight to the glorious end, nor do I fault Fissoa or Astrum for coming to terms. Eponllyn has both accepted terms and decided to fight to the bitter end, at different times (yay, we survived our fight to the bitter end!). The various Vales of Beluaterra have alternated between the two extremes, as well. Neither fighting to the end or accepting terms to survive another day are bad in and of themselves. As long as the path is engaging to the players of the nobility. I suspect more players were lost while they were only sitting in the city, not actively engaging the enemy. Letting them rot and starve doesn't increase player engagement.