Thanks for getting back!
The object you linked to is one that seems to have been changed at some point to 32bit IDs -- is that what you need for testing? (Can't tell when you downloaded it) Or objects that are according to your specs (with group 0x80000000 and long IDs)?
This might be interesting to test with: catalogue objects for kitchen cabinets/counters, the workingness of which (with the in-game model selection and all) also depends on the ID -- I don't remember the details exactly but I believe they needed to have a group ID of 0x00000000 in order to work. Might be good to check whether or not this kind of thing would work with 0x80000000 as well. The instance IDs of that are 64bit. (The "No-Drop" package is the interesting one.)
This is also old, with group 0x80000000 and 64bit IDs. Or
this or
this or
this.
--
A remaining problem might be that as long as the design-tooling goes by the MODL ID, people can still stick different objects in the same thumbnail and the design tool recolouring procedure will not be able to switch between them .. IDK; would it be possible to give them a somewhat more interesting failure message than "Script Call Failed"? Something along the lines of "You can only redesign between variants of the same item" .. ? (Or can this be made to work too, perhaps? I seem to recall that in the pre release CAS demo there were some pants in the same thumb that were actually a different mesh .. but then that's CAS, not objects.)
