If it had been picked up in mid-1980, you'd be having to deal with the fact (presuming you want this thing to run at least five years) that your returning actors are all a decade older than the characters they're playing. (They just barely
got away with that in TMP.) You'd be right back to the budget limits of sci-fi network television, which would fly in the face of TMP's visual FX standard. James Doohan suffered a major heart attack around that time (if I recall right), which would have disrupted production further.
If mid-1982, it would've definitely been "no Shatner, no deal." They still would have had to recast Saavik (thanks to Kirstie Alley's blockheaded agent demanding too much). George Takei would be grumbling about wanting to be captain of his own ship (relegating his role to an occasional guest appearance). And again, you'd be having to try to put out TMP/TWOK-quality visual effects on a Battlestar Galactica
-sized budget (at best).