It could be fun being the proprietor of a department store in space, especially if they're relatively rare.
The BMM is clearly not the best choice for any of the professions that exist in game now. It's a bet on the medium-to-long-term future, a ship that was $250, is now around $600, and might be worth $1000 eventually - if you believe some of the hype (not sure I'd go that far...).
The 'shopkeeper' aspect of this ship is its main role, and clearly more of an aspiration than something we can evaluate now. Whether it is something a player would want to do depends greatly on whether the devs can design, implement, polish, balance and maintain a fun game loop that is interesting and profitable enough to keep players participating in it. I believe they can. But we haven't heard much about that yet, and it's likely years away from being finished, so I'm reserving judgement. Who knows - it might be great, it might be boring. Maybe you could take your BMM somewhere dangerous, with an escort, stock your various shops up with rare/valuable goods, then move somewhere much safer and highly-populated, park up, let the NPC shopkeepers have footfall from some NPC customers, and afk or log. Maybe you'll be making a reasonable profit while you sleep. Or, maybe that won't be how it works and you have to actively manage everything as a sort of mini-game. Speculation isn't worth much, right?
I just like the ship, a lot. It's huge, and from what we've seen so far it looks utterly beautiful. Arriving somewhere in one, you should feel like you're really making an entrance.
This ship is not primarily for combat, though it is well armed and supposed to be able to fight, but obviously it is not going to win against similar-sized military ships. Nor is it primarily about cargo hauling, though it can carry a very respectable volume of cargo. It could be good for the high-end passenger touring/transport profession when that's a thing. Maybe BMM owners need to turn up at in-game events (monthly pilgrimages, festivals or parties, at some some remote station on a moon) with just the right combination of rare commodities in stock for the travelers to buy? Maybe there will be commodities in the game loop that are low-volume, command a high profit margin and which you can only sell direct to NPCs, and not in bulk to a TDD. As a player-owned ship, I think it's a long-term bet on something that is possibly more useful for having fun and travelling in style in the short term, and a hypothetical retailer profession in the longer term, and less useful for min-maxing in any one profession that will exist in the short term.