Also need to look further into the BBK mounts.
From this pic the plate stops before the mount bracket.
There must be interference with the bracket that it cant extend further.
On the E46M plate in post #5 above, it looks like its designed to extend all the way to the caliper.
In order to do this the caliper bracket would need to be behind the plate.
.....more investigation definitely required as there will also be variances depending on mfg.
Safe to say though that there will be some compromise either way.