(answer cloned from Nuclear Hoagie, then expanded and somewhat quantified.)
If your Ceres is "booming mining hub, supplying water-ice and cheap minerals to other destinations in the solar system", then you want the cheapest and easiest way to lift all those resources off-planet. erm, off asteroid?
Sure the Escape velocity of Ceres is only 510m/s, but that is still delta-v that needs to be paid for. So if you could get it for free, why not? And if you could get some more velocity for outbound cargo containers for free, double bonus!
A CeresSynchronous orbit around Ceres is only 722 km above the surface. So if you build a Space Elevator, the center of mass need only be at or very slightly above this altitude. A heavy orbiting rock near this altitude serving as anchor for a space elevator would serve as an excellent base.
Now for real planets Space Elevators are tricky things. You have atmosphere, and slow rotational speeds, and huge gravitational wells. This imposes such demands on the elevator tether material, that you end up having to build your tether out of exotic materials and with a ridiculous taper, resulting is a very heavy and expensive construction.
And the elevator could be made out of ordinary steel, much less any fancy material!
With Ceres' feeble gravity of 0.27 m/s² , and a tether length of only 722km, you could even use a Kevlar untapered cable and have a strength margin of more than 2-to-1. A Decently tapered cable (someone else calculate please) should give an even better ratio.
Similarly, you can extend a cable from the anchor rock up to as high as your material science allows you. At least several thousand km. And cargo allowed to whip up the high end cable will exit it with a completely free velocity of a few km/s.
You can even use the outward acceleration to generate power, sacrificing some speed for a lot of energy for your system using very simple linear induction motors.
So: Your rock orbiting Ceres is the massive anchor for a Space Elevator to lift bulk cargo from the surface. Its mass provides stability to the system. It provides an excellent zero-g storage, manufacturing and staging area. It also serves as a similar anchor for outgoing cargo slings, and possibly for power generation from these slings. It is effectively a Port City for a rather large country. With all the support infrastructure, housing, entertainment, bureaucracy, crime, and everything else that a big port City has.
And all you lose is the initial construction cost, and a microscopic amount of the rotational inertia of a very heavy (10^21 kg) Ceres.