I have been in contact with a supplier that is in process of designing and will be offering a super detail brake kit for the MP4/4 which will have CNC machined calipers,and brake hats, fittings & parts to enhance this fantastic kit.
The cost is estimated to be in the 170-200.00 range US. As to not break any forum rules you can PM me for further information, I will inform the supplier to make him aware of this forum as well. I have purchased his other products and they are very well made, high quality.

I have discussed the probability of builders already have mounted the calipers, and this is response from detail brake supplier, you WILL be able to retrofit the super detail brake kit to your model build even if you have already glued on the calipers to the hubs:

I completely understand everyone’s concerns especially about the calipers. We will provide two options: 1. Would be to remove the calipers and we will provide new mounting pins. The hole locations could be drilled on the uprights and the old pin locations could be drilled out on the back of the calipers. 2. We will be offering new machined calipers and, again, we would provide an easy and accurate way to mount them. It is our responsibility to address this and provide a couple of easy solutions for those who would like to use our products to upgrade their McLaren. it might also be possible for us to provide new uprights or any other parts needed to make the change. We’ll do whatever it takes.