Hi, we finally went live today so a small summary of how it went. pppoe(4) did not work. We need to authenticate with chap first, then pap. pppoe(4) forces the exclusive use of either one or the other. This was an unexpected gotcha and I will look at the code to see what can be done.
pppoe(8) worked fine so we are using it for the moment. We did use the debug option when diagnosing the issue with pppoe(4) as you suggested but tcpdump on the physical interface was much more comprehensible. Hope having this in the archives helps someone else as google is rather poor at returning useful results...