Borg Assimilation question

[aelius]

Hi all, new to the forums.
I have been looking at the Menagerie rules and wished to create a species like the Borg.
So far I have Cybernetic (of course) and Adaptable, for 3 points.
I also gave them Hivemind for 0 points
I have Xenophobic and Superiority Complex, for -3 points.
That leaves me 2 points open which I plan to use for Assimilation.
That's what I wanted opinions on.
I was thinking that you would treat it as Extermination in game mechanics but have it cost 15 or 20 points per Census and instead of killing them they become Borg. Like enslaving the populace only worse. And more efficient. No revolts. But it would have massive negative diplomatic consequences. Not that the Borg would care about that, what with being superior Xenophobes and all.
Whatcha think? Should I make the Assimilation ability cost 2 points or raise it to 3 and drop the Adaptable? Also any comments on the Assimilation ability itself would be welcome. I think it is as close to Borg Assimilation as i am going to get within the framework of a playable race in VBAM.