The client limits the valid spell IDs.. somewhere set in the client.
Currently the source supports all clients max spell ID range.. but you would have to figure out what they are.. unless someone else knows them :p
The only things that look like they would be unsupported for all current clients is... "IsBlockedBuff" and.. "IsBlockedPetBuff" .. because they are only int16 and RoF2 goes higher than that in spell ID range
