here is my vote on this, sorry for the late reply.
1) Should we accommodate crossover cables, i.e. take either polarity of power? (more cost in the PD)
in order to save cost, let's accept straight through cables only, Six diodes per port
cost & mount, that will sleep after a detection --can we justify this cost? for we detect once in a long time
2) Should we require having a non-linear component in series with the signature resistor for discovery?
probably not necessary, we may leave this open for any gotchas- Murphy type in the future...
3) Should we pick one and only one pair at this time to send power?
If yes, then pick one: 1236__X___ 4578__X___
I think we have graduated from the pair school, and with a Phd....
4) Should we specify power for both pairs, with the second pair being optional for higher power?
Yes, I would say since power can come on either pair, and one day someone out there may want to
run his oven over Ethernet, why stop-em from getting the power on both pair at the same time,
and if they did, do we care... would we know - possibly the 802.3 police might give em a ticket...
5) Should we leave open the possibility of using the second pair for power in the future?
Again given that Autopolarity MAYBE out, we save at least 8 diodes, now another resistor for
detection and some ORING diodes can possibly give flexibility and may be something that
is good to have...
6) If we were to allow power on both pairs,
should we make discovery on each pair independent of the power on the other pair?
Yes, the 2 pairs should be independent