Here’s a thought I had — perhaps 0-12-26 is inherently an even more flexible formula than 5-12-26, because you can use magnesium nitrate instead of Epsom.
Veg: you run the recipe using magnesium nitrate in the same amount you would normally use epsom with 5-12-26. This brings your nitrogen back up.
Flower: you run the recipe using epsom. This drops your nitrogen back down how you’d want it when you normally use 0-12-26
I’d have to run the numbers through hydrobuddy, but I think it would work out pretty close to ideal.