I added in a couple of extra races into SFC 1 here as the game engine seems to allow it, so long as it complies with the ?-FF, ?-CL, etc. thing.
The minimum needed for a race is obviously freighters / merchant ships and some sort of naval warship to protect them such as frigates, cutters, corvettes, skiffs, etc. all under the FF size vessels. This would work for a less advanced just developed warp drive race with most likely Drone A / PH3 / Disrupter 1 maximum technology. I added in a few such home brew races, one without even warp drive, just for something to conquer with the Klingon Empire.
The thing is, with home brew races, is to have a ship design theme / ethos / style unique to that race's starship development tree.
Disrupters are a spin off of particle beam cannons so would be perhaps more common than phased energy weapons.
I invented a more advanced foe for the Klingons to conquer / have border disputes with (on the away facing border from the SFB "core") called the Eln which has a complete navy including monitors.