How do I set custom resolution for text-only mode

[szatox]

I'm looking for a way to stuff more lines on my screen in text mode. Increasing resolution with vga=773 kinda works, but it doesn't really fit that funny panoramic display shape. And it only get's worse when I turn it by 90° to get 9x16 instead of 16x9.
I wonder if you have any ideas how to force some equally funny resolution upon text console. E.g. something around 900x1600 would do. Obviously it is far from any standard so there is no vga mode for this.

That particular system I have in mind is running on qemu inside windows. Without hardware boost. I still want to get more lines on the screen without pushing half of the qemu frame out of the - oh, irony - window. And no, ssh is not an option. Nothing that requires network access is an option.

So.... Ideas?