Better Ornaments with Accidentals

As a result of the discussion here:
https://musescore.org/en/node/316664
I found it's necessary to make such a feature request or improvements in the future Musescore, probably 4. The current way of applying accidental(s) to an ornament is quite non-standard, only staff text and extra symbols are available, except for the trill line which we can add an accidental, but this is still not accessible due to the inspector issue. Also, this way doesn't automatically generate correct playback unless adding a hidden voice. The Musicxml output, except for the trill line, is also impacted. If the input accidental is a symbol, nothing will be exported at all. Sibelius can do this by just putting an accidental symbol on the ornament. and the xml export is correct. But there's another issue for the turn, where some accidentals are below turns. So should we improve this function by:
1. Unify to use accidental symbols from the master symbol palette, and apply correct playback/Musicxml output. The negative value of vertical placement determines the symbol should be below a turn and plays the altered lower auxiliary note, putting a "placement='below'" at the accidental-mark tag of Musicxml.
or 2. Implement extra things in the main ornament palette as accidentals with ornaments, both above and below, so that blind musicians can simply apply them without having to adjust vertical placement at all (staff text and symbol need this all the time). This will also give correct playback and Musicxml export.

Haipeng