I guess I've been stubborn about this change long enough. As many of you have already noticed, the guns of Wilfred's tank are drawn in a different perspective from the rest of the parts. It was impossible to keep the same persprctive as they couldn't be rotated correctly that way - guns would raise and lower the barrel instead of turning around. But now everything will change.
Behold my new, fully 3D ballista! Enough of ugly perspective mixing - now everything is displayed and rotated as it should. And it still fits existing visual style.
So, how did I came to this? I was drawing a new base with a slot for long-planned, but still not implemented big guns, and I suddenly realized a few things: the size of the new slot breaks the perception of perspective much more than in the case of regular guns; I still can hardly imagine how should I draw the catapult planned for this slot in the existing perspective; and that I can’t do the intended way of attaching one to another within two dimensions in any perspective. All together, this was a sufficient reason to finally go learn how to create 3D models.