If I want to say "the ANCIENT CATS are aliens", emphasizing the "ancient cats", but in an unmarked way, then how do I it ?

If I just write {novmey bIH vIghro'mey tIQ'e'}, then the {vIghro'mey tIQ} is topicalized by the {-'e'}, but not emphasized..

In an unmarked way? You can't, using pronoun-as-to-be.

But you could say nov vIghro'mey tIQ'e' the ANCIENT CATS are alien.

-- 
SuStel
http://trimboli.name