TBH mate, the idea of valve/solenoid controlled 2nd fuel pumps sounds
quite over complicated...

also. once you go to Throttle bodies or turbo or whatever your plans are.. you wont want to go back, so wouldnt worry about it!..
Add to that, the fact it would be way easier to make a 2 line system back into a 1 line system (change back to old pump and block off return)

I would just change it all for the proper fuel injection stuff, and worry about changing back if it ever came to it.