I've done something similar to the first pic, except I had the MLT on the bottom. The HLT would drain to the MLT via gravity, then the pump would recirc the mash and drain to the BK which is on top. Then, your sparge water is added to the mash via gravity and the process is repeated. You could also fly sparge that way if you wanted to.
This way, you only need one pump.
If you go with the concave HLT, you should be fine. Cleaning is NOT an issue, just make sure you have a bottom drain so it will drain completely. Then you can wipe it out with a paper towel. Also, since it would be custom, make your sight gauge plug into the bottom of the tank so you can measure the whole volume.
The concave tank is actually clever insulation. It should decrease your boil time and keep your mash temps more stable. If you're worried about heat loss to the other vessels, throw some reflectix in between and your HLT will get to temp faster.