From exploring it, I've found that minor races often research the 'defense' and 'weapons' technologies (on Normal difficulty and below- as I said- I did some research).
In DA, I created about five Customs that were, in fact, minor races given a name and super ability.
Things I do not like about minors:
-They build mega amounts of starbases, on resources and influence, which don't help them.
-They block their ports up with constructors or weak ships.
-Their planets are valuable, and if I have no 15s, who do you think I'm going to invade?
Now, in some Civilization games, 'minor races' were civs just like the 'major races' but they were not playable.
So? Make a mega event where minor races recieve colony ships and start colonizing! (to make it fair, they should get all planets in the sector they own)