Thoughts on modding unit caps for high cost, T5 units?

I was looking into making a building/recruitment overhaul mod (primarily using unit costs to determine tiering) and I was thinking about adding unit caps to HE star dragons to rectify how all 3 HE dragons arguably belong in T5 based only on cost. That way HE would have T4 sun dragons, unlimited T5 moon dragons (I'm aware they're going down to T4 in 7.0), and limited T5 star dragons.

However, this got me thinking about the other T5 units over 2000 gold cost, and I was wondering about other people's thoughts on what other units could justify similar unit caps. Which units do you believe are at a point a tier above T5?

I'm guessing the Dwarf **thunderbarge** wouldn't be too controversial in getting capped, considering it's the most expensive unit in the game and a flying warship.

LM **Dread saurians** already have unit caps, but I would move the trained one to T5.

Empire **steam tanks** cost 2100/2400 depending on SP/MP. They are alone in their building, unless landships are raised up to T5. I could see limited steam tanks with unlimited landships at T5.

Ogre **thundertusks** cost 2300 and share a building with the stonehorn (harpoon launcher) unit. Unless stonehorns get buffed and recosted to rival thundertusks, I'd op for unit caps on thundertusks for now.

Bretonnia **royal hippogryph knights** cost 2200 and share a building with royal pegasus knights. On paper, I could see adding caps to the hippogryphs, but I don't have a lot of experience with Bretonnia.

Chaos has their **toad dragons** and their **mutalith vortex beasts** at 2100. I could see an argument for the vortex beasts, but I really can't see limiting the toad dragons. Even the vortex beasts are much more vulnerable to shooting compared to something like a steam tank or thundertusk.

LM **ancient stegadon (engine of the gods)** is the most borderline of these units at 2050 (2000 in mp). The regular ancient stegadon is so strong, I tend to see the engine of the gods version as a sidegrade.

As a side question, is there any idea why the Empire and Dwarf warmachines are so much cheaper in SP? I thought it was common for missile units to overperform in SP over MP. I also didn't realize how many of the LM big dinos are priced up in SP. The coatl and engine of the gods I can understand (vortex/wind ability + big AI blobs), but even units like ripperdactyls and carnosaurs have increased prices.