4X in space, you have an Empire. When you conquer planets you also get alien population. They become part of your Empire, but not exactly as full citizens (you can change this by edict).

Question, how to call these citizen levels (need like 5-7 levels)?

Example:

1) Full citizenship (typically only your starting race will be of this status)

2) Limited citizenship

3) Resident/Freeman

4) Slave (I don't like that one)

I like the 1 & 2, but the lower ones... Plus I need a few more than 4.

You should add in plebeian. It's fun to say and not overly demeaning.