I much prefer to talk about the young ladies of that era, rather than the guys.
Back to "Day of the Dove": I always assumed that if the Pinwheel Alien had the ability to transmute phasers into swords and to alter the ship's decks so they could not be cut-through, then it would seem possible that it would have the power (or find some way to harness it) to stop the aging processes of the corporeal lifeforms involved.
If there's a big plot hole in the episode, it is in explaining why the Pinwheel Alien went to the trouble of getting the Enterprise to destroy the Klingon ship, then take the Enterprise on a high-warp Flying Dutchman out into isolated deep space, and then cause the ship to fail in the middle of nowhere. What would happen when the power and ship's supplies ran out? Humans and Klingons both supposedly need heat, light, gravity, food, water and waste treatment to function properly. Cut those support services off and they "will die in the icy could of space." I imagined that the Alien had a destination in mind; maybe a far-off planet where the warring crews would fight while the starship would fall out of orbit after all its systems would fail, isolating Kirk and Kang and company indefinitely. That's the only way to make sense of it, at least as far as I could see.
The episode is flawed, and the only way I could see to make the plot flow more logically would be to either do a Neural-like situation where the Alien would be caught manipulating warring factions on a primitive planet. (Of course, this would be similar to "A Private Little War"; but then "Day" is just a re-write of that premise anyway.)
The only other way I could see this alien-instigated-war story being brought to life more sensibly would be if there were a story arc, spanning multiple episodes. It could work, but it would have starship battles and armed landing party confrontations instead of sword fights.
Regardless of how the story would be written (or how it was done), the biggest weak point of all is how Kirk and Spock were able to find the alien and corner it. Something that sneaky and powerful would seem to be impossible for its victims to confront. So no matter how you look at it, the whole story concept suffers from some serious plot holes.
Despite all that, Kang and the other Klingons in this ep were great. Too bad they didn't have a stronger story. I thought it would have been great to see a cut-throat drama with swirling intrigue involving the Klingons, the Romulans, the Enterprise and possibly other aliens after some Holy Grail as well. It would be great to see Kang and the female Romulan Commander at first conspiring to thwart Kirk, then turning on each other and less-advanced aliens pulling everyone's strings by falsifying messages or planting bombs or something like that.
