Well, I mean, it could work and would be an interesting experiment for sure.
Grow is 2-1-6
Micro 5-0-1
Bloom 0-5-4
So when you add those up in a 1:1:1 ratio you get a final fertilizer with a ratio of 7-6-11. That's probably an okay recipe for the most part, especially with additives; any cannabis fertilizer you want to make sure that N is less than K and P is less than N, so that ratio will do it.
Also, with those additives make sure you're using them very sparingly. This may be a bit of a minority view, but I don't think anyone has ever truly had an insufficiency of calcium or magnesium, basically all the cannabis products I've seen have sufficient micronutrients in their base products, especially using tapwater which is usually high in calcium and nitrogen. I think most "cal-mag" supplements are sold in bad-faith because this stuff is pretty complicated without an understanding of organic chemistry. I think what usually happens is people feed N and K in excess, which both lock out Ca and Mg ions from being available to the roots. The problem with adding "cal-mag" if you have a magnesium deficiency is that most of those products have a ton of N, which locks out Mg in excess, so it's sort of not doing what you want it to do and adding more only makes the N-toxicity worse. Confusing stuff...
Granted, some product lines are formulated to include a calcium product that is necessary on top of the base nutrients, but I think General Hydroponics already includes enough Ca and Mg for cannabis in the Flora Trio. TaNG is a master-grower and has some amazing results on here, but like you said, I think using the Advanced Nutrients lineup, so it really is a different beast.
If you do go forward with the 1:1:1 ratio, I'd really be interested in the progress! The other 'easy' way to use GH Trio (duo, really) is called the Lucas Method, where you just mix Micro and Bloom in a 1:2 ratio for semi-soilless medium or 2:3 ratio for coco coir. I found leaving out the Grow sort of caused more problems than it solved, so I went back to using the 3 part formula.