This is what I did to make the CV a BA:
1. Use the console DI command and get your CV ID number.
2. Save and Exit game.
3. Go to the save file for your game, make a backup copy of the save directory, then to the Shared subdirectory.
4. Find a file and a folder that start with CV_Player_ followed by the ID from step 1.
5. The file is a txt file so open it in an editor like Notepad++
6. Change every "CV" to "BA", save and rename the file CV_Player_ followed by the ID.
7. Rename the subdirectory CV_Player_ + ID to BA_Player_ + ID.
8. Run the game and load the save you just modified.

While in creative, you then have to remove everything that is CV specific. So all thrusters, the CPUs, pilot seat, etc... Everything that is specific to a CV has to be removed if you want it to be a valid BP to spawn in a game.

I'm curious how you made it register as a Base instead of Capital Ship. Something with changing the type of Core installed?