Alex - funny, you find them firm? To me, just the opposite (Kent & Keitt are firm...and of course, TA). I do agree they are not alternate in Florida however I already made my statement regarding the shy production.
They have a tiny amount of fiber that most people don't detect that gives them some degree of firmness. Similar to Kent in that regard, but the skin isn't as thick and that's the drawback.
Mangoes with softness qualities like Carrie, Bombay, Cogshall etc...these are in the category of essentially 'no firmness' and aren't really suitable for high volume commercial production. They are suitable for 'local commercial' though.
Edward's biggest drawback for large-volume commercial is that it just doesn't produce that well in comparison to the established commercial cultivars.
One thing I forgot to mention is that Edward does have superior fungus resistant qualities to a few of the other commercial major commercial cultivars.
Overall though Berns, I have to side with not recommending Edward for commercial planting. There are lots of better options that are more profit-friendly.