Hello,
in V7 we introduced a material manager inside Proxy - It should be much more user friendly to assign materials (there is a limitation to multiple material assignments with different mappings, we're going to look into that for V8). This should allow you to not duplicate material Tags and assign materials directly to material layers.
I re-made your scene using the material manager and I can clearly see that proxies are rendering bump (not correctly though). It seems that the UV mapping is extremely off in some cases (e.g. the buckle logo in example scene) - I will create an internal task for this.
We are planning to improve this proxy material manager in future daily builds, most likely to include sublayers for individual UV mapping, UV mapping GUI, ...
I cannot promise any ETA, sorry.
Thanks,
Jan