Funnily enough, the talk of expanding the passenger missions looks like a request to level up an already established feature.

In general, it's worth reiterating that It could be fairly said that there are still some major outstanding features that are yet to be implemented at all, so again, it's a case of development resources / time. Pick your favourite feature you would like to see be put into, or expanded within, the game and then go from there - nearly all parts of Elite can be improved as a matter of objective fact and the list to things to add isn't short either. But of course, not everything can be done at once and priorities naturally have to be assessed and followed to the possible chagrin of anyone wanting x or y feature to be implemented/improved but getting z instead.
It's kind of why I think Frontier mentioned overhauling an established feature, Odyssey brought a substantial new feature to the game with the onfoot aspect, not forgetting the bonus of light atomspheric worlds, so maybe Frontier are looking to take that long standing feature to the next level as an intermediary step?
It sounds like having proper NPCs in the game would be a popular choice, and being a feature of ambience rather than direct gameplay probably easy to overlook compared to others. Having said all that, I would actually very much welcome an overhaul of NPC interactions so as to include the things mentioned above and other things such as dialog tree interaction - it would be great to see the NPC foot traffic expanded.
Though it has to be also said that this would suit best to be Odyssey exclusive as effectively the request is to expand upon the main feature that Odyssey delivers the first iteration of - in game onfoot players & NPCs. Whether one would consider that to be a bad thing or not, I don't know, I would suggest that it would be best viewed as adding more value to the Odyssey expansion, providing another reason to keep supporting Elite's development by purchasing Odyssey, as Frontier would be providing something of substance that surely would be worth rewarding, no?
Still, when one thinks of watching passengers boarding a ship the blue circle teleport would most certainly need to be reworked into a boarding ramp with the teleport part set inside the ship slightly off to the right of the on ramp entrance, so avatars and NPCs are look like they go up and turn right into the ship, leaving visual sight, with the suggestion that they are toddling off to their chosen quarters etc..
I like the suggestion a lot, the more I think about it the more I think it would bring a lot of 'life' to the game that would be of benefit to it.