This is my idea, but if you have better and more practical ideas just share them. My idea would be to simplify how to write the embellishment, mostly we are all confused often on how the composer wanted us to play. Do we start the trill from the same principal note, above or below, sharp or flat? But why don't we make things more simple? Mostly when we play these ornaments we have only three note: the same principal, the one above, the one below. So, instead of writing symbols why don't we write letters. We just need three letters, s-u-d, and we just combine them. s=same note, u=upper note, d=down. The speed of execution is done simply according to taste, but that's going to be always natural and obvious, the duration of the trill can be prolongued with the usual zig zag sign, and the sharp or flat are just indicated like we do always in a turn symbol. Here are my example pics, let me know what you think, it would be very useful to unite for this.