...agree with you 100%; on what "our" Klingon ship should look like in this Prime Alternative Verse...
And, as luck would have it, my PA design partner, Ricky <MadMan1701A> Wallace, had already designed and built his own Klingon Warbird; to do battle with Our Enterprise!
Ricky said, "he based his design on the Klingon "Warbird" that was seen in the Kobyashi Maru test in the 2009 film.. with a merging of style cues from images available in the book "Star Trek: and The Art of the Film"
see Ricky's Orthos for his Klingon "Warbird" here
I think Ricky's "Warbird" is an Awesome Design; and it really works as a perfect match with Our Prime Alternative Enterprise ...what do you think?
Battle II wallpaper link
As for your question about a Romulan BOP; I agree with you on your statement that...
"the TOS version BOP doesn't really look much like anything that came from Romulus before or since... Enterprise's version actually comes-off as a better predecessor to the TNG Warbird. And it doesn't help that we never saw a TMP version of a Romulan vessel"
Ricky and I had discussed at length a PA version of A Romulan BoP back in 2011; and we have a bunch of design drafts & notes for our "Balance of Terror" ship; which I think could turn out really well...So, after getting your post this morning, I pulled them up and started getting excited about it again... so, maybe I can convince Ricky to build this one next!