Personally I think a fretboard needs to have a compound radius to play the best. I just don't see how a Plek treatment can achieve this without shaving off some frets to the tang. The way I see it the strings are converging from the bridge to the nut. As such they lie closest against a CONE and not a CYLINDER.
Somebody needs to invent a machine that resurfaces the fingerboard to these dimensions and then guitar is refretted.
That may seem the case but it might not actually be so. Unless you're trying to put a tight compound radius into the frets themselves without touching the board, there really shouldn't be very much material removed either way.
Think of it like this: if you have a 12" radius board and you're going to get the frets leveled and you want them leveled like a compound radius board but you don't need the radius at the nut to be too far off like 7 1/2" or something, then the leveling procedure is fairly simple. You just use your leveler in the paths of the strings instead of keeping it parallel to the center of the neck like you would with a cylindrical board.
If you want to really change the radius then you would need to reradius the board and refret, but just leveling in the paths of the strings puts a slight compound radius into the frets themselves without touching the board and only a very slight amount of material needs to be removed to accomplish this. Luthiers and techs did this for years without realizing it's what they were doing, and there are a lot of older guitars out there with single radius boards and slightly compound radius frets from this kind of work.
When you think about it, if you level like a compound radius neck on a standard board then what you're really trying to do is establish a flat path on the fret tops under where each string lies. So if you think of a single radius board as being like a glass cylinder and the string as being a straight edge resting on that cylinder, the straight edge will only be in contact with the whole surface if it rests parallel to the center line of the cylinder. If it moves to one side or another, the ends are no longer contacting the glass and the straight edge rocks back and forth on the center.
Strings that are closer at the nut than they are at the bridge are like that off center straight edge. So to get the surface under them flat and true, all you need to remove is the small amount in the center of the cylinder that is making them rock, so to speak.
Picturing a water glass may make this seem like a lot, but on a cylinder with a radius as big as a fretboard it's really a tiny amount. In fact, according to one of Erlewine's books the amount you need to remove in the center when reradiusing a board to be compound can be as little as .003". I personally have always removed at least that much from the overall fret height on all the frets I've leveled, and on a normal modern fret that's .045" tall or higher losing .003", either overall from a normal leveling or a little extra in the middle to make them compound, is not a lot. And as I said, luthiers have been doing it for years with no ill effect.
This has nothing whatsoever to do with the PLEK machine, I just thought it was interesting. It's easy to think of a compound radius as being a really small, tight circle at the nut and flattening out to almost totally flat at the end of the board but in reality it's really a matter of thousandths of an inch.