To make the world more enjoyable/believable they would need some additional graphical assets like people walking around in the background, more different advertising panels, better system and planet descriptions (which are fitting to the products and minor factions available there), more audio speech (shouldn't be a problem to record the npcs talking with some employees right from the office and using some com distortion), usinf the commanders name in the mission description, multiple chice answers, let some npc buggies travelling around the planetary stations, some news about cqc (why isn't there a youtube channel dedicated to it in the art of an sports event - think american gladiators style) etc.
For real gameplay changers they need an fps-part/walking around in the stations/on planets with some stealth mechanic included. Only with that you can truly put some life into the game like smuggling deals in bars, security controlling / patrolling gateways if you are wanted / wearing some not allowed weapons, getting gossip from the bartender, hacking / breaking in in some building to steal some information, search for missing people, assasinate people, getting attacked from thugs or bounty hunters, enter a stranded / drifting spacehulk for loot, check out some abandoned planetary base, make a trip in space outside your ship to repair some components etc.
Plus rich populated worlds like Earth would only allow you to enter the planet in a specific corridor and land on a specific part / platform (if not they shoot you down in good old Elite fashion). Access for spacefaring folks would only be allowed for some tradehub, maybe with some instances for special missions you get teleported to.
Possible to do, but would basically require a second game. Awesome if they could make it. I hope it will be but I doubt they could pull this off. At least they have some experience with fps by developing such a game (unfortunately it never got released).
EDIT: the crafting in Horizons seems to be rubbish. It's basically magic potions and alchemy in space. And how much the buffs provide it will basically become mandatory. Seems to be as bad as I thought it will be