I saw
this ship recently and was reminded of how as a kid I thought something like this ship was probably part of the Klingon fleet. That the Attack Cruiser we saw was not the Battlecruiser's replacement, but simply another kind of ship in the Klingon Defense Forces. And that maybe an earlier version of it was around in TOS and could show up in a flashback to it.
Did anyone else think this? Does anyone else have similar memories about ships maybe from when they were kids or before they saw more Trek?
I also thought that there were newer classes of Klingon Bird-of-Prey as well. That we just happened to visit an old rust-bucket when Riker did the officer exchange in "A Matter of Honor" maybe in part because the Klingons didn't trust Starfleet near newer technology.
Good topic!
So the reasons why we never saw new filming models of Klingon ships at the start of TNG were the same reasons why we never saw new filming models of (contemporary) Starfleet vessels or space stations:
1. The producers didn't want to waste budget money building new models if the show wasn't popular and got cancelled, and
2. They had both stock footage from the films and five usable filming models from the movies (The Enterprise-A, the Excelsior, the Reliant, the Grissom and the Klingon BoP.)
For the Klingon ships specifically, they used both stock footage of the K'T'inga class and the BoP from the movies, and later used the BoP model for new shots of generic Klingon ships, but now upscaled to a much larger size than was originally intended, as they didn't have a new large Klingon ship model yet. The two biggest offenders of this being the ships from "The Defector" and the K'Vort class from "Yesterday's Enterprise" (both episodes were before the introduction of the Vor'cha class.)
While Michael Okuda recently posted a photo of his kitbash of the K'Vort class that he offered to the VFX people (but was subsequently refused in favor of reusing the BoP at a larger scale), at least it was an instance where someone thought that a different design than a movie model would work. But for "The Defector," it was problematic because that episode already had three brand-new filming models debuting in it: the new 4-foot Enterprise-D, the 2nd Romulan warbird model, and the Romulan scout ship. There wasn't money in the budget to create a new Klingon ship for the episode as well, so they just upscaled the BoP to ridiculous proportions. I personally would have used the Promellian battlecruiser for that shot, with the ship standing in for a Klingon vessel, which was what actually happened in an episode of Deep Space Nine.
Obviously if I were in charge, I would have built a new large 24th century Klingon battlecruiser and used it as early as "Heart of Glory" (where they just used stock footage of an out-of-date Klingon battlecruiser from TMP). But unlike the link you posted of a custom-built model, I wouldn't have painted it green. I would have kept it the bluish-gray of the K'T'inga, since they already established that 24th century Romulan ships were green. I also would have abandoned the bird motif and went with something different, for the same reason. Actually, I would have given it Starfleet components (like the nacelles) to emphasize the Klingon-Federation alliance. FASA had something similar back in the day:
https://memory-beta.fandom.com/wiki/K'mirra_class