ZDoom

We have nearly everything to emulate Software Mode's looks, from the palette to SW banding and Software lighting mode. But we don't have a way to emulate Software's sprite clipping mode. It's either have the sprites float above the floor (Always, Smart, or Smarter) or have the sprites clip into the ground and lose some some rows of pixels (Never). Would it be feasible now to have this mode implemented for completion sakes?

Sorry, but this simply isn't possible. The only engine ever to implement an emulation for this is Strife VE, but the method it uses is incompatible with nearly every advanced GZDoom feature.

Alrighty, got'cha.

Can't even do something a bit more cheaty like how UE "projects" the sprite forward towards the camera?

That'd cause all kinds of different glitches. In the end it just boils down to the simple fact that you cannot cheat the depth buffer and there's currently no way to do advanced depth checking in the shader yourself. You could surely try some workaround but they'll come at a steep performance hit mostly.

dpJudas attempted it before but concluded that it was trickier than he initially thought.

The other thing is that if it were done by some sort of cheat/hack/trick, I can guarantee that it would then become one of those features that generate years worth of bug reports for unusual maps and other edge cases that people feel should be supported because the feature is now "official".