I just noticed a draft RFC, which is somewhat relevant to this thread:
http://tools.ietf.org/html/draft-ietf-v6ops-6204bis-10It only requires prefix delegation support on the WAN side of CE routers, it is not required on the LAN side. The draft doesn't even mention the possibility to have prefix delegation support on the LAN side.
In short we shouldn't expect chaining of routers as discussed in this thread to work with IPv6, if that draft is what vendors will follow when designing CE routers.