It could be problem because its a HD wallet, so although the PPC keys could be stored separately from the normal key tree, they could not be explicitly recovered from the seed (which would be fine because they can be recovered from the NSR keys). Sounds a little bit hacky though.
Another solution would be to implement a feature that sends all the peercoins on the corresponding NSR/PPC address to a PPC address within the wallet, at the cost of the tx fee of course.