Drahk would need a colony or two to be able to make deals, while raiders could be purely nomadic pirates.
I reccommend giving Raiders some sort of "Capture Ray", to make ship captures easier. It would be a range one, low damage, "only living beings" damage type, Surgical Strike weapon.
IE. it takes out crew quarters, boarding parties & security teams only.
It will be weak enough to only destroy one component per turn, so you'll need to attack crippled/unarmed ships, use a larger ship to cover you, or use lots of raiders.
Aside from those advantages, they will also have the advantage of depleting the "shields" generated by the advanced armor & grav deflectors.
APPEND:
Back to nomadic stuff: Raiders make their money from capture/scrapping, drahk make their money... how?
As for maintenance... what should the values be? (They can be anything we like, despite the 5% rule)
Raiders will need to be in the 0.5% to 1% range, in order to be able to maintain ships.
Also, a "civilian cloak" would be useful as a racial tech. (Hide in plain view, and all that

)
How to give arbirtary maintenance costs:
We can set all ship hulls to give a 90% maintenance reduction.
The raiders take 5% maint, 10% of which is 0.5%
The normal races take 250% maint, 10% of which equals SE4 Classic 25% maintenance.
[ 15 January 2002: Message edited by: suicide_junkie ]