You've got two basic issues. 1: If it's sporting grav sensors for jump points, then it's military, and 2: if it's military it suffers breakdown (if enabled). As such, carrying a few cargo modules for a mine, some infrastructure, and a construction yard should enable you to take any colonists in cryo, put them on a world, harvest some basic materials and produce some maintenance supplies. A high number of maintenance spaces will also help keep the failure rate down.
The other option is to have another ship for grav sensors, which would require a hangar (and make it military) or a tractor beam, where the tractored ship is still subject to decay.
So, all things considered, it looks like you'll have a proper arc. Orbital Habitat will allow it to be constructed by industry and thus you can make it any size, but it also disables jump drives due to the enormous size. The OH also allows N/A cost worlds to be short-term productive for purposes of mining and resupplying. 5 cargo modules per desired building, such as a mine and construction yard requiring 10 cargo, plus a few to carry loose minerals I'd say. Several cryo pods too, obviously, to support the workers needed. Infrastructure carried and deployed will support some, and the OH will support some as well. A very important massive passive sensor is a must, since this will be a non-fighting ship and needs to see threats far enough away to avoid them. If you could fit a few boat bays and carry some probes to fly through a JP and check for enemies then you could avoid possible ambush, but you'd also want to tow a small shipyard to produce more in case they're lost. Small shipyards aren't terribly heavy, especially compared to the OH itself. I'd suggest hangars anyways as you'll doubtless need some quick scout ships to go survery bodies and JP's. You can also mount a buoy with a grav/geo sensor, put the buoy as the second-stage for a drone, and then fire the drone at a desired location, allowing it to survery from afar. You can also mount a thermal sensor on a buoy, in a drone, and deploy some eyes far out. If you're wary of a jump gate, fire a buoy nearby and let the buoy's sensors tell you how dangerous it is. For that you'll need a fire control of some type (doesn't have to match range if you're firing at a waypoint, so it can be a small firecon) and probably some magazines, as well as ordinance production loaded into cargo (will have to set down on a planet to activate it).
The more I think about it, the less likely it seems that one ship will be enough.