The only reasonable way to make an imported object snap-able is to convert it to a Morph. You can change the appearance of any surface at that point as well.
After import and conversion, see this for clean-up:
http://helpcenter.graphisoft.com/tips/removing-triangulation-from-imported-sketchup-cinema-4d-and-3d...
See this to change the surface appearance:
de/virtual-building/construction-elements/morphs/useful-commands-for-transforming-morphs/custom-face-settings/
etc.
If you need an object - to be placed multiple times or in other projects - vs a Morph group... then just save the morph(s) as an object after you finished fine-tuning.
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