In my opinion use the pump to move from mash tun to kettle. That way you can keep your mash tun nice and low where you can easily mash in, stir and check temps-it's the only vessel that you really do much hands on stuff with so make it easy to use. You can also see the water level on top of the bed easily when fly sparging if your vessel is low (if that's how your going to do it).
Put the HLT above the mash tun if your going to gravity feed somewhere on your system as you don't really need to look into that vessel, fill it in place with a hose from the ground, reach over and give it a stir every now and then but put your pump to good use in making your brewery easy and ergonomic.
Cheers mate. Justin