Some may remember when I first arrived to this site I also took a partial crack at rewriting the Atlantis Invaders. I do tip my hat that you finished it entirely, Maurice. I really enjoyed reading the annotations.
I do have two general observations about the original concept for this episode, the first being that I don't know what came over the Johnsons in the early days of this story. I assume that the early drafts for the Mighty Galvanaut, and Atlantis Invaders and all the others were brainstormed around the time they did the Savage Empire. I'm just surprised they still went ahead with setting Atlantis Invaders in an ocean environment, complete with an army of alien mermen and even one scene with Garrovick hanging on for dear life to a sea serpent as it swam to the surface. Gotta admit they were really ambitious at the time, but professional film studios with an actual budget would have shied away from such a story. Did they ever concede a lot of those ideas were too difficult to pull off, to put it mildly?
The other aspect that still bothers me somewhat to this day is that they brought in the characters of Princess Tr'tillya and her father, King Argolas into their series. Not the characters themselves and their purposes in the story, but rather that for a ''show'' set in the 24th century and one that strove to strictly emulate what may be the most socially-conscious series of the 1960s (for civil rights, women's rights, anti-war, etc), yet would be casually validating a concept as ethically despicable as generational rule well into the future.
I may be wrong, but I think that apart from the episode Elaan of Troyus there was never a mention of another Federation member planet that had a monarchist system, though I'm still puzzled that such a forward-thinking organization would even accept one that wasn't a democracy. But since the Troyaans were portrayed as near-barbarians who still developed interplanetary travel somehow, astoundingly, I guess the whole point of that episode was for Kirk to be completely frazzled by Elaan's barbaric ways, and a monarchist system was a simple way to make that point.
But I guess as much as we may have evolved over the last 500 years we are still unable to sever completely with the romantic but intellectually heinous images of Kings and Queens and Princesses, especially since corporations like Disney make those their bread and butter. But apart from children's animated films and most British costume dramas, you can notice how portrayals of royal characters have been progressively absent from most serious modern-day set entertainment for the last few decades (though not from medieval fantasy projects like Game of Thrones and the Witcher or garish comedies like the Princess Diaries).
Just look at the trouble Marvel Entertainment had with its house concept the Inhumans series which deservedly got trashed and canceled quickly. A Royal family of artificially endowed super-characters should NOT be one with its own film or TV series, only guest appearances at the most. You can't really make heroes out of a family that controls who gets the superpowers in the kingdom. Of course it's going to be the close cousins and nieces and nephews who will inherit the best powers, while everyone else will only get utilitarian skills...because that's how the family keeps the throne for itself. and the writers can't make any OTHER characters/serfs from the kingdom ones with an interesting personality because eventually you HAVE to write a story that has them question WHY they can't have a better power (answer? because that would reveal the Royal Family of the Inhumans is not such a heroic bunch after all).
Anyway I've been meandering in different directions, but basically I would have hoped that the Johnsons should rethink Tr'tillya's royal status entirely if ever this script gets salvaged. I'd like to think someone like Gene Coon would also have changed that aspect of the script.