Simplified Music Notation

I don't think it'd be feasible to create a hybrid with traditional noteheads with sharps & flats (and double sharps & flats). Music has a key signature because the notation system is diatonic based so each key is a distortion of C Major or its modes. Any music you write is generally considered to be based on one of 12 (or 15) diatonic scales which are alterations of 'white keyboard notes' (themselves not immune to alt spellings) and then have to be distorted by accidentals unless the music sticks to the diatonic scale determined by the key signature. I use the Simplified system for shorthand (hand-written). The noteheads can therefore be considered to instead refer to keys on the keyboard, like a tablature. No need to remember accidentals (or think about key signatures that might not even underlie the music particularly well). Similarly, rhythms can be restricted by the difficulty in writing them down and by tempo changes. Probably one reason early western music did not develop rhythmically to the same level of sophistication as harmony is the relative difficulty in writing rhythms down. It encouraged simplicity or uniformity, in my view. I think a free graphical rhythmic notation would compliment pitch notation, for some musicians.

With regard to the specific noteheads, you don't need to hold key signatures in mind and then think what's been altered. The notehead shape tells you the keyboard key in one symbol. Shape-note notation is not a new thing, actually, this method just applies alt noteheads to 'black-key' notes.