At work we have a script/settings that let's us do this with the arrows keys. We use plus/minus to change the snap amount and page up and down for z movement, so it should be doable. Combine that with the standard snapping and you pretty much have something to what you want. Unfortunately can't share the script but I doubt…
You could write a script that automatically creates and destroys a grid based upon the normal of the selection you have enabled. That way you'll get arbitrary angles.
Interesting read, I will have to try this out. It definitely works well but needs to be fleshed out for now. Only work with edit poly on, or not at all (but not both at the same time). With some fleshing out this script could be really useful. Damn just made it feel like it is possible but doubt we'll ever see it.
Unfortunately the other thread didn't exactly find a solution either. The reason i do not enjoy moving an object to 10,20,10 for example, is because I believe these numbers are floats and can become innacurate. For example if I push a vert of box to 10,20,10 and the same for another box. The 2 verts won't actually line up…