The more famous case is surely the famous cry ''eloi eloi lema sabacatani'', designed to explain (to the stupid hoi polloi) that Jesus was not invoking Elijiah, and so the Spirit who abandoned him on the Cross was not the same spirit who possessed John the Baptist. In other words, that the Christ was not John the Baptist.
So I think that the introduction of Joseph of Arimathea serves precisely the same pattern: someone was identifying the Christ (or the Primal Man) with the Patriarch Joseph, so that someone had to be silenced astutely. It was not Christ who was ''buried'' in [=who possessed] the Patriarch Joseph, but viceversa: the patriarch Joseph 'buried'/'possessed' temporarily the presumed Christ.
Et voilà: the invented ''Joseph of Arimathea'' was the literal ''owner' of the body of the presumed Christ, even if only for a short time. The message addressed against who identified the Christ as ''embodied'' in Joseph, was therefore the following: please, don't enumerate Jesus among the evildoers.
And for who in this forum is not able to derive the correct evidence from Hippolytus (and does so only because of a mere contempt of the Gnostics), here is the evidence:
This, he says, is he who appeared in the last days, in form of a man, in the times of Herod, being born after the likeness of Joseph, who was sold by the hand of his brethren, to whom alone belonged the coat of many colours.
http://gnosis.org/library/hyp_refut5.htm