This is very simple script I did for "fixing" proxies in 3ds max 2014 and up.
When working with a lot of proxies in 3ds Max 2014, viewport gets very very buggy. The problem is when "preview from file" in VRayProxys display option is checked. So this script finds all the proxies in the scene and changes then to "preview from file (faces)" which seems to fix this viewport problem!
Script will not make any changes if some proxies are grouped.