Amortizing the investment is possible if the plan is for several seasons that are 10 or 13 or 17 episodes long, whatever the writers deem to be the right amount needed to tell the story for that year. If the show is made for streaming, you don't even need to worry about the number of episodes to fit the network schedule, it's wide open,
The anthology idea could be as simple as having a large ensemble cast that all interacts in a certain location - planet, space station, spaceship. Characters can be killed off and new ones introduced.
The old broadcast TV notion that you must keep certain characters or actors because people watch the show for them, is one of the rules that can get thrown out on cable and streaming services. You might have one central character and everyone else is expendable, or maybe you kill off the presumed central character too.
I think the core characters that you need are :-
Chief Medical Officer
You might have those as core roles, but there's no reason a certain character can't be killed or transferred or otherwise out of the action and a new character introduced. New roles/characters could be introduced too, not limited to standard Starfleet ranks.
It would really raise the stakes to have a show where no character was sacrosanct. In practice, I'm sure the writers would recognize when they have a great actor they shouldn't kill off lightly so the audience will probably catch on to which characters are unkillable for that reason.