Upload & Sell: On
The old conventional wisdom (when the 1Ds/1DsMKII was the only body used), was to modify lenses, as only a handful reguired modicfication. This got to be pretty hairy, as some of these were multi-thousand lenses that were having their re-sale value permantly affected.
You are the perfect example of the 5D conundrum that no one believed- the 5d mirror is all over the place for reasons that no one knows. With the camera being the device that becomes obsolete faster, it now makes more sense to modify that, and leave the lenses alone. Great German glass holds its value well, and I intend my arsenal to be my last lens collection that carries me through to retirement. (providing I continue to use EOS mount cameras).
If all you want to do is use one $300 CZ28/2.8, well, then use it on the body that clears. If you plan to acquire a collection of the best of the best, then modify your cameras.