I have an Acerbis fuel tank on my 2006 KLX250S. It has wings similar to the KLR tank that extend well below the carburetor inlet.
To get at all the fuel, I did something like what you are contemplating with the exception that I used a snowmobile fuel pump. They are vacuum operated. The system worked perfectly (for a while).
Tygon tubing was the issue. It is formulated for gasoline, but I didn't realize at the time that it isn't formulated for alcohol. After a few months, the tubing swelled up and the brass barbs (weights) on the ends of the tubes fell off. Actually, only one did, but that was enough.
I returned the system to stock for a while then decided to redo it with Viton tubing. That worked, but now there was another issue. The KLX is my secondary bike and it sometimes sits for several weeks before being ridden. I always drain the float bowl if the bike is not going to be ridden for some time. In order to get gas into the carburetor, the bike has to crank for a very long time. The fuel pump doesn't have a high volume flow. I would find that I would sometimes exhaust the battery before the float bowl would fill and the bike would start.
Obviously, if the bike were ridden regularly, that wouldn't be a problem.
So, once again, I returned the bike to "standard" mode. Surprisingly, I've found I can use fuel in the wings well below the carb input level. The Acerbis tank has a center well where the petcock is. I guess just normal fuel sloshing fills this well from the wings.