It is my understanding that PPPoE is just PPP wrapped in Ethernet packets. PPTP is PPP tunneled over GRE/IP. So, my question is, is it possible to take incoming PPPoE packets and easily rewrap the PPP inside as PPTP? What I want is for a PPPoE-aware device (such as most home routers) to be able to speak PPTP transparently through another device which "translates".
I've not seen conversion done between PPPoE and PPTP, but things along that line are doable -- I've seen a setup where we had an L2TP tunnel to another ISP, where they proxied the PPP(oATM, I think?) from their customers over the L2TP tunnel, which terminated the PPP session on our RAS.