I know what you mean with the t-valve, we use exactly the same thing on our hydraulic setups on farm machinery. Works well as the pump has no extra back pressure as overall flow hasnt changed, and if you get a needle valve, like something off of a propane system, its very minutely adjustable. You could of course just make it ebb & flow, with the addition of a simple timer for not very much, or you could put an inline T-valve to your existing set-up, and change the flow to the plants. This would be the trickiest set-up to get right, as too much would waste nutes and flush the pots, too little would kill them, and this amount would change over time as the plants grow, plus would be different plant to plant. Dont to that one.
The timer would work pretty well, me-thinks, just set it to run for long wnough to fill the pots up as needed, and leave it alone. I think it assumes that you have return lines to your nute tank though, I wouldnt imagine that they are essential, as not reusing water would mean that as long as evaporation was minimal, the EC or Ph in your tank wouldnt change drastically.
The bypass t-valve would be pretty easy, fairly fool proof, and you know if its not working. Would be a very simple system to do, but still relies on your input every time they need water. Unless of course you do a bypass valve, with a timer....
I dont grow anything in hydro, but can you tell I want to?