Merge objects to single mesh

[StjerneIdioten]

Is your feature request related to a problem? Please describe.
I hate to do 'destructive' modelling. That is to make a permanent change that I can't go back and redo in some other way. So fx. when creating nuts/bolts on a model I like to have it modelled separately and then place it using instances or dupli's everywhere it needs to go. But when exporting, this results in having a huge number of shape nodes in the scenegraph.

Describe the solution you'd like
A way to define a "merged mesh group" sort of like merge groups work, but for merging into a single mesh upon export. So you can model parts individually , but in the end turn it into one mesh without having to destructively merge it with your main mesh (in the case of nuts/bolts)
This would of course mean that any I3D settings should only be able to be set for the root node.