Looks like a good transcription, though I wonder how many people will
use it exactly. We certainly should not judge people's scholarly
credibility or level of Hebrew knowledge by how well they stick to any
scheme.
Why don't we get rid of the digraphs completely by using X for heth
and C for tsade? Also I would suggest using J for teth, which will
always be a problem but at least it looks like a T with a hook on it.
With these changes we avoid having to worry about keeping upper and
lower case separate. We can also then more easily use doubled letters
for dagesh forte which is much more intuitive than dots for dagesh
(and is hardly a very complex rule for beginners to learn).