In fact Origin is capable of handling Poly-aftertouch messages. In fact, the "Pressure" modulation source (that can be seen in the Progr/PERF page) corresponds to either the channel (mono) aftertouch or the key (poly) aftertouch, according to which is received.
Origin keyboard (and, starting from the 1.3 which is released today (!), Origin Desktop as well) has a duophonic aftertouch feature that allows to transform channel aftertouch into key aftertouch. But it does not send poly-aftertouch messages, only channel aftertouch: the duophonic feature is only for the audio kernel and is not transmitted outside.
So it would still be possible to assign PolyAt messages to parameters, but that feature does not seem to be so interesting: how many devices use this non-standard convention? Creamware could have used RPN and NRPN which are a more standard way to extend the number of available parameters...