I like the idea of getting started with the fertilizers.
I would make a recipe that is the same ratio and amount that the water in the tank would end up with, but just barely use any during the dry start.
So, if the goal is NO3 level of 10 ppm, then make some water with that much, and so on with all the other ferts.
Use this water to top off as needed.
STS has high cationic exchange capacity, and will be removing fertilizers from the water, and holding them ready for the plants to use.
The young plants, with the roots not yet spread through the tank will not be using much fertilizers right away.
You are pre-loading the substrate so when the plants are ready to grow the fertilizer is there, waiting for them.