This is a fun little mod. If you can fight them, being able to use one of their ships isn't gonna imbalance anything.
ThinMint, I experimented with the domain drones first. Most of them don't seem to be worth it but the Rampart and Defender are both decent if you have the Front Shield Generator modspec. I use two shielded Defenders as escorts for my Apogee(D) and they managed to survive a hectic REDACTED fight. The Rampart is not great, but it's a brick with large ballistic mounts and sometimes that's exactly what you need.