I agree that base building is a good idea. Frontier have said it's not on the roadmap, but the coming of Odyssey really does make player-owned bases compelling.
However... They would have to offer things that Fleet Carriers don't, otherwise it would make much more sense to just park your carrier in orbit as at least you could move that if you changed your mind. I'm thinking this difference should include mining, as it would be great to be able to mine Tritium by building your own base on an ice world (as an example) or gold and platinum on a barren world out in the black. Frontier would need to balance the cost of running the mining operation with the value gained from the materials being mined. It can be done, but would require a lot of thought to avoid being outright exploitable.
Then there's the issue of durability. Fleet Carriers are indestructible. Bases would also need to be indestructible (surely, right?) in order to be similar, but what would this mean for the building of turrets, and the deployment of security drones?
I do love the idea of being able to build a base over time. Let's face it, Frontier have a history of building exactly this type of game. I really hope it happens, as I'd love to have a small base that expands into a fully-fledged outpost, complete with its own NPC and player factions, or even a Tritium mine in the centre of the galaxy to help refuel carriers.
My thoughts.
I see people compare carriers with planetary bases. Why?
It's not remotely the same.
If you only gonna look mechanics-wise, then maybe yes, you can park your ship at both locations, but they're not the same experiences.
Surely there'll be people who would rather call their carrier a home, but others would prefer to call their planetary based real estate a home.
For a number of reasons, I wouldn't compare them.
Just IMO.