The ideal UV filter will have absolutely no effect on your pictures. It would be the same as no filter at all.
Anything less than ideal (real world) may degrade sharpness, introduce a tint, or add flare to your shots. Aside from the first two, my guess is that if you're shooting under conditions where the filter is gonna flare, your single-coated lens is already gonna flare quite a bit anyways.
So you're adding the potential for more flare (assuming no sharpness or tint effects). Is that what you want? If you want even more flare, use an uncoated filter.... heck, stack 'em and see what happens!
Zeiss Ikon, Nokton 35/1.2 v1, Nokton 50/1.5
Neopan 400, Acros 100, 160S