D143 is a great product and it is non acidic, however in concentrate it has a high pH range of 14.5-15.5. A 2:1 dilution does not reduce the pH very much. An original pH of 15 at a 2:1 dilution will bring it down to 14.522. At 4:1 the pH comes down to 14.3 and at 10:1 it's down to 13.96. I used it at 5:1 and I always wore gloves and a mask if it was a breezy day.
Wow I didn't know it where that high alkaline D143. That's extremly high ph level and as you mentions even if it's diluteble it don't get much lowered ph level of them afterwards. I would say if you have wheels that can handle both D143 and D140. D140 is not that acidic ph level that you would think as it's ph4.5-5.5. So think it's actually more gentle to use D140 than D143.
Another option to go with could be the Meguiars Wheel and Iron Decon D1801. It's ph neutral and it seems to be haveing a high part of the iron remover ability in it. And for maintance washes of the wheels you can test to dilute it to 1:1-1:2 and I think that you will see it works great in that dilutions also. Then just useing a car soap in the wheel bucket to get if any other dirt and grime it don't take off to be enough with the added car soap and aggitations getting it clean. Also it would be way more gentle to your wheel protection if you have that. Say that the RTU D143 has a ph14. This would be very harsh on any protection even on a ceramic coating has trouble to stand up to that kind of ph level. So the RTU or diluted D1801 would be very gentle to the wheel protection than the D143 and D140 IMO.