I would say any kind of TOS-era space station would have to have built-in hard-docking-ports. What if there are technical difficulties with the transporter? Space stations, just like any other space vessels, would have to be designed to handle any contingency including an "abandon ship" option of shutting the place down and leaving it. And if you ever had to come back and reactiviate it, a starship might need to re-power it and board it using a docking port.
"The Ultimate Computer" (non-remastered version) makes it clear that an entire Federation starship's crew can (somehow) be disembarked from ship to station, and that the crew can (apparently) stay there. This, combined with the presence of Starfleet brass and V.I.P. Daystrom, should make it clear that such a station has plenty of room and creature comforts. It also seems (to me, anyway) to at least swing the door open a little further about the existence of 22-person transporter rooms. (The ones standing in line for "This Side of Paradise" were likely the last crewmembers after everything else had been shut down.)
I'm not too sure I agree on the discussion about K-7 and the grain. Whether K-7 was being used to temporarily hold the grain until the weekly freighter came to pick it up, or it was being held there for some procedural reason (needed to be subject to some kind of treatment, needed to be check and approved before being released to Sherman's Planet, whatever) K-7 may be serving a purpose it was designed for: to harbor valuable cargo until it can be either processed or traded or simply picked up. It could be a standard use for stations like this. This would seem to be backed up by the station's obvious personnel uses: shore leave, shopping/trade, a platform for official business, etc.
I suppose that either K-7 or the unnamed M-5 war games station could be located just about anywhere in Federation space, from inside a star system to an interstellar void. If such a station were located in orbit around a planet or moon, how difficult would it be for a station of that size to keep the orbit from decaying? The only advantage I could see to a station being in-system is quick access to a nearby planet and free photovoltaic power from the star. (But if your station is using transporters and subspace transmitters all the time, wouldn't that kind of usage demand the same kind of power generation that a starship uses?)