If the pumps have check valves the check valve will close when one pump looses pressure(sucks air) so you should still have pressure in the fuel system. This is with teeing the pressure side. You would also need to arrange the jet pump system to work in this configuration to your advantage. As far as burning a pump up running it dry it shouldn't hurt the pump considering it would no longer be under load and drawing very low current.

Staged systems have to have check valves on the secondary pump(s) if in parallel.

I will have to test this with the stock pumps. "T"ing up top would be much easier.

What is your opinion on a 2nd pump being always on, and always feeding fuel into the driver side basket?

Basically wiring it up along with the driver side original pump

I had planned to use a switch to control it but would simplify my life to have it just be always on, if there were no drawbacks

I would probably just use two stock pump baskets teed with two controllers parallel. You could put a filter (or sock)on the crossover tubes and run them to the back or side of the tank.
3d print some flapper doors or buy.

Best would be build a surge tank that replaced the basket then a factory basket feeding the the surge tank.