I decided to re-suggest this feature only now because I noticed that recently it has been added a 'bump' in pcbnew version for an internal field of the footprint ...
So I thought that it could be easy done an other small change for a nice improvement...
It could be something to be added only when opacity value less than 100% would be present ...
this would break back compatibility but ONLY if transparency is applied (opacity less than 100%).
No need to change all the footprint libraries
(at (xyz 0 0 0))
(scale (xyz 1 1 1))
(rotate (xyz 0 0 0))
opacity field added to footprint ONLY if its value is less than 100%
That small addition in the footprint parser will be an useful feature addition for the 3d-viewer.