It's best to order the Mothership to "Hold Position", although AFAIK that only works with an NPC onboard. The AI of the Mothership alone only tries to follow the Player; at least that's how it used to be.
AI alone will hold position, at least it has every time I've tried it.
Once 25km Range is exceeded, any AI order will be overridden by the Mothership attempting to get closer again. Hence it's best not to exceed this Range while in the SLF if feasible.
That did occur to me but I've never put it to the test. As soon as I get a range warning I head back.
One annoyance, more visual than anything else, is that the autopilot will always turn the mothership to face the SLF unless docking has been requested. It makes it quite awkward to get beauty shots of the mothership from various angles unless docking is requested, at which point the docking hologram can spoil the aesthetics of screenshots. Nothing major, but it's on my mental list of "tiny QOL tweaks" that I might get around to writing down one day.
(It also occurred to me that this undesired rotation could be risky over very high-G worlds, if the AI pivoted the mothership to follow the SLF and slid off the enhanced vertical thruster axis. I'd like to believe the game is designed in a way that would prevent this, but having seen an underpowered mothership destroy itself in an attempt at an automatic launch to orbit with disabled thrusters (bad priority settings) I wouldn't want to put it to the test. I tend to avoid very high-G worlds anyway.)
Crew members steal your exploration money
That was my primary consideration when I first started exploring, although with the current payouts I could afford a hold full of NPCs and still be raking it in. It also bothered me a bit from an RP perspective; because I have two accounts I explore intermittently, a few weeks on, a few weeks off. It didn't seem reasonable to expect another pilot to (a) join me on a months-long expedition to God knows where and (b) be prepared to sit around for weeks on barren moons, waiting for me to decide where to go next. If the game were hyper-real, I'd expect to log back in after a month's absence to find my NPC had trussed my CMDR up in the galley and stolen the ship.
On a more serious note, the only thing that would make me consider taking an NPC exploring is if I could see them in one of the flight deck seats. That might be on the QOL list too, although it's more of a "nice to have" than a "would be better if it wasn't" sort of thing.
