For some reason, I have it in my head that in the early concept phases of Star Trek (what's now known as the original series), the idea was that the saucer section would detach and land on planets. This was later deemed to be too expensive to film, and so the transporters and shuttlecrafts were introduced to the scripts instead.
I like this idea because it gives some reason why the Enterprise is shaped the way it is: it was originally intended by Gene Roddenberry and the model's designer to be a flying saucer for planetary travel, coupled to a warp drive and engineering section that stays in orbit. The idea is that the saucer section and its landing gear were retconned as emergency features once the idea of regular saucer landings had been nixed.
The question is, is this story actually true? That is, is there any evidence, from interviews, memoirs etc., that regular saucer separations and landings were ever part of the plan for the series?
(Note: I'm not asking about in-universe information from technical manuals, scripts, or even the series bible, since those would all have been written after this idea went out the window - I'm asking instead for out-of-universe information about the early development of the series, before any scripts were ever written.)