I personally think 2 Overlords at 1k is a little much, I would consider using the smaller one that comes with the barge as a standard lord, gives you a new buff and is cheaper. Might give you enough points to add a couple warriors to one of your squads.
I think your Immortals are good with tesla, Gauss is a far more aggressive weapon
imo. Your warriors cover the front lines marching midfield while your tesla immortals sit on objectives.
If you wanted to swing in the far other direction for your immortals a 10 man squad of gauss when paired with an
HQ (say, a lord

) with the veil of darkness can be quite a lethal combination relatively speaking.
Other than all that I think you've got a good list, the detachments should blend well from 8th to 9th, you get 9CP now and when the switch to 9th happens it'll all fit in a battalion so I think youre set