Hello!
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.
HOORAY! REJOICE!
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).