The problem with the idea of a Voyager
-like TOS spinoff is that it would've been kind of redundant. The premise of Voyager
was meant to be about getting back to a TOS-style series, with the ship and captain off in the wild frontier and being entirely on their own rather than constantly calling on Starfleet for help and guidance. (Which, ironically, was what TNG itself was originally meant to be; that series started with the Enterprise
-D at the most remote Federation outpost in existence and travelling outward from there. But almost immediately, you had the E-D helping another Starfleet ship in jeopardy, delivering a vaccine to a Federation world, and so on, so that premise never really got started.)
Not to mention that Lost in Space
was already on the air, so a Trek series about a lost ship trying to get home would've seemed very derivative.
A DS9-like premise could perhaps have worked. After all, the idea behind DS9 was to do The Rifleman
in space, analogously to how TOS had been pitched as Wagon Train
in space. So it would've fit right in to the Western-dominated TV landscape of the '60s. Although it wouldn't have had the serialized elements that DS9 had.