Hiya, just got back into KSP and have started work on the moons with Better Tourism, Bases & Stations, and SCANsat. I think I've tracked down why I'm not getting any base building missions.
The "BaseScan" contract type seems to have a dependency on a SCANsat part no longer in use. The earliest (on the tech tree at Advanced Electrics) hi-res radar altimetry part is now named "scansat-sar-paz-1". I believe that part name should replace "SCANsat_Scanner2" in the REQUIREMENT:NEEDS[SCANsat] section of BaseScan.cfg.
With that fix, the BaseScan contract can be completed and the BaseRover contract becomes available. I think BaseRover must be done before BaseCreate is made available, because BaseCreate seems to require a rover specifically built for BaseRover. BaseRover requires that there's no rover on the body, but with the new contracts available from Some Assembly Required, the player is given free rovers to repair all over the place. An easy fix is to change the vessel type after the repair rover contract is done, but maybe the requirements in BaseRover could be loosened a bit, or perhaps BaseCreate could require any rover, not just the BaseRover rover.
Hope this is helpful, and thanks a thousand times for all the great mods you're keeping alive, @linuxgurugamer!