Would it be grammatically wrong to say the following ?

jaghpu'    chaH    chaH'e'

enemies    are    they

I know we could say {jaghpu' chaH}, but my problem is, whether it would be grammatically wrong to say too the {jaghpu' chaH chaH'e'}.

Ungrammatical. No, there's no rule against it, but it's obviously not said this way. The chaH is NOT the verb are. It's the pronoun they, them. In Klingon, pronouns are not verbs, even when they are the center of a copula sentence.

jaghpu' chaH romuluSnganpu''e'
As for Romulans, enemies them.

Nothing is happening in this sentence, and no condition is being described. This is an identity. Identities are handled by pronouns in Klingon.

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SuStel
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