Just a question and perhaps a caveat. What is the execute key for the expansion function? If it's something like the space bar or a full stop or comma etc, then you are inevitably going to run into the steno's nightmare, which is having an abbreviation which is a "real" word. My best example is days of the week/months of the year. I use the first three letters, but words like Sat, Sun, Wed, Jan, Mar, May, etc will crop up in the course of ordinary work, and if your execute function is attached to the space bar then you will have unwanted expansions occurring.
One solution is to make your abbreviations text strings which are unlikely to pop up - which means you have to be able to see well into the future to know for sure. The other way is add some sort of marker eg #Jan, #Wed, to make the abbreviations unique. This was what I did in 1990, when my first employer was using Hewlett Packard Word. But as you can see, this adds an extra keystroke to every abbreviation, which tends to defeat the idea of abbreviating.
However, if, as in my own system, you have the capacity to tie the expansion function to the keystroke of your choice, then that's not a problem. This is one of the reasons I chose WordPerfect over MS Word, because in both programs, the expansion function works on the space bar, and other punctuation marks. But whilst I could re-assign the expansion function to my own key in WP, it was not possible (at least efficiently) in MS Word.
As you have observed, I have a bias towards legal because that's the work I do. You will have your own row to hoe in that respect.
Have fun.
Joe