I was finally able to find something really really... golden. Jackpot! It's the Battle Realms Widescreen support hack/fix/patch and a program that changes Field Of View in the game (even on 4:3/5:4). I've decided to inform everyone about this amazing find, so here you are.
Update as of September, 2019: New and improved version here.
Since the "Custom Resolution Patch" made by fk. doesn't work properly, this is exactly what people have been asking for.
Attention: Works only with Winter Of The Wolf (A.k.a. 1.50q a.k.a. the latest GAME VERSION since 2002).
Now if only my PC is currently working well and not being fixed at the shop, I would be enjoying this FOV fix right now. Any bugs encountered so far? It sounds like it's bringing up a whole new possibilities of editing the UI of Battle Realms. I think a more minimalist approach would be a good way to modernise the UI (think Sins of a Solar Empire or RUSE).
Well, since the game wasn't originally designed to work like that, when you change fov (or in every game beginning), it shows black borders on the map, but they dissapear once you move the camera to any direction, so I can hardly call it a bug. I means it's a 1 second bug, that doesn't ruin anything.
I do believe if the creator was able to mod the FOV, it's possible to find the camera rotation that was present in the earlier game versions (and maybe is still locked inside BR, but that's not confirmed).
I actually wanted to mention the authors, but wasn't able to find the names and then got carried away, I mentioned showing support towards the authors in the instructions (both rus/eng) inside my repacked archive. :)