I agree post-ENT would be the most interesting because the show could be about literally the first class of Starfleet Academy, all these young people from various species really coming together for the first time and figuring out how to coexist and work together all while the new, integrated Starfleet is coming together around them (and dealing with all the growing pains and teen/young adult drama that comes along with all of it).
But it's probably going to be set in the new DSC era.
If it turns into a teen drama it'll be a absolute dumpster fire of garbage.
The baseline assumption you have to make with an academy series is that you can't assume just because someone is young that they are irresponsible vapid people who are looking for cheap pleasures.
The mission of the story has to be out to prove there are real depths and strengths that come along with youth.
If you watch Lower Decks and pay attention to the Seto Jaxa arc it is simply amazing. She goes from a kid busted for doing a daredevil stunt, to a someone who stands up for herself and ends up doing the ultimate sacrifice.
To me it makes sense if you have duality between the campus instructors and the students.
The instructors are more gruff, burned out from living on ships and want to take it easy on earth.
They are moving on and wish to pass the torch to a younger generation. One of the more tiresome themes in trek is the idea that everyone more or less is in their early 30s or at least acts like they are in their early 30s. It'd be nice if age could be explored for more than 2 episodes a season.
Not in some hokey young people have fun old people are boring type of way. But more along the lines of older people are starting fresh on earth as instructors, older people who are trying to move on from their past mistakes, people who are interested in nurturing the younger generations.
It'd be nice if we had more of a master craftmen apprentice relationship going on. Much like we saw with Obiwan Kenobi and Luke Skywalker.
You got a bit of this in the movie Dune. The lead is a black slate who is suppose to be the chosen one. While the older people like guerny are painfully aware the kid is not ready, and know they won't be around to make him ready. Those tensions for me made Dune amazing it was so refreshing. Instead of propagating this fantasy that age is an irrelevant part of life.
I'd also add there'd need to be a great importance placed on field exercises. Obviously to keep it from being boring, but also because it would help in exploring some of those intergenerational ideas. We've seen a great deal of this with O'brien and Nog.
Also it should be noted that not everyone at the academy is 18. It'd be interesting if we had non com's or just life long slackers trying to start their lives over at the academy.
I do also think it's important to really lock into the idea of youthful ambition. We the audience are seeing everything for the first time and so are they. They should be the naturally gifted types but also the ones without experience. The instructors should be the more relatable people who've had to face their limitations more directly. I.e. Similar to early Bashir versus late seasons O'brien.
It also has the ability to be more realistic in people's appearance. You have an obvious sex appeal with younger actors, you don't need to handpick that 1 women who at 25 can play an role of a 35 year old, while at the same time looks like they are 20.
T'pol comes to mind as the pinnacle of this. Her counterparts are in their 40s and she's in her 20s.
If you want sex appeal have characters that make sense. Have them being the junior officers.
The flip side is hiring women who are actually in their late 40s early 50s, who actually look like they are in that age range.
For me it is just not credible when all your women have to be played by women in their 20s when their roles on the crew should be played by people in their 40s.