I think a system of tablabure is usefull for any diatonic instrument. It's form will be different for different instruments. What is important that it be standard and used by every one in the same way. There is such a thing for guitar and harmonica. The one for harmonica consists of arrows and numbers. An up arrow means "blow" and a down arrow means "draw" The number of is the number of the hole. (There are several ways to denote "bends" and things like that.)

Let me use the harmonica as an exmple. Suppose you learn to play "Mary Had a Little Lamb" with a "C" diatonic (eg Marine Band) harp. Now that can be written down in standard musical notation and it also manifests itself as motions that you go through to produce the tune. (Blowing, drawing, moving from hole to hole, etc.). Suppose you are going to accompany a singer with the tune and they find it falls into their voice range better in the key of "F". What you would do is put down the "C" harp and pick up an "F" one and play the tune. Your lip, toung, hand, etc. motions will be the same as on the "C" harp. However, the musical notation will be different. When you work through the notation, of course, you will find out that you should do the same thing on the "F" harp as on the "C" harp, but the tablature has told you that directly. You can pick up a harp in any key in your collection and follow the tablabure. You will have the same tune in the different keys.

Chromatic instruments are a different story. There every note corresponds to some physical position (fretting, closing holes, etc.) If you want to play something in a different key, you use sharps and flats to modify the key rather than a different instrument. There the musical notation gives you all the info you need.

There is an alternative for musical notation in diatonic instruments. You can use a "transposing system" as used in single reed wind instruments and horns. I prefer simple musical notation for the rythm and tab for the tune.

Murray