pfsync and PPPoE redundancy

[Taylor R Campbell <campbell+netbsd%mumble.net@localhost>]

(I am not subscribed to this list, so please cc me in replies.)

My home gateway is a single machine running NetBSD, using pf for NAT,
with one ethernet interface connected to my ISP talking PPPoE and
another ethernet interface connected to my LAN.

                                          / hosts
(ISP) ---PPPoE--- (gateway) ---ethernet--<  inside the
                                          \ LAN

I would like to replace the gateway by a redundant pair of them, each
with one ethernet interface connected to my ISP talking PPPoE and
another ethernet interface connected to my LAN, so that if one goes
down -- e.g., when it crashes, or when I upgrade the operating system
-- the other can still provide service.

                 / (gateway A) \              / hosts
(ISP) ---PPPoE--<               >--ethernet--<  inside the
                 \ (gateway B) /              \ LAN

We already have carp(4), so that gateway A and gateway B can share an
IP address on the LAN.  In NetBSD 6 it seems that we'll have pfsync(4)
too, so that gateway A and gateway B can synchronize pf state (perhaps
over a dedicated third ethernet connection between the two gateways,
on interfaces separate from the ISP and LAN interfaces).

I have three questions:

1. Does pfsync work yet in NetBSD-current?  It's not in any GENERIC
   kernels.

2. Can gateway A and gateway B share the PPPoE state so that this
   setup would actually work?

3. If this would work, any suggestions for cheap, small, low-power
   hardware for gateways A and B?  Preferably under $150 apiece (and
   ideally, that would include any necessary CompactFlash storage).
   The Soekris net45xx/net55xx and the PC Engines alixNdM look
   plausible, but I have no experience with them.