What sort of cost difference is there between a jacket and getting the exhaust housing ceramic coated? Would ceramic coating work more effectively and reliably?

If the turbo is getting so hot that it seizes, it would imply that you are relying on radiation to keep the turbo cool, which would imply you need a better cooling system for the turbo - perhaps a post-turbo rad to keep temps down and/or a dedicated electric pump circuit for the turbo?

Chris