unusual dual-WAN and dual-LAN config puzzle

[Zaphod Beeblebrox]

Hi,

I would like to set up my most unusual network configuration yet. I haven't yet purchased routers and I'd like your advice before I do to know if this is even possible.

I have two houses, each one with a LAN and a WAN connection:

House 1
LAN
ADSL WAN

House 2
LAN
cable WAN
​

The two house LANs are connected by a wireless bridge via TP-LINK CPEs (TL-WA5210G).

I would like to set up my network so that if one WAN connection goes down, BOTH house LANs will automatically fail-over to the other one. I'd also like it so that when both WAN connections are up, BOTH house LANs will load balance between the two WANs.

I'm guessing that I'll need one router in each house with a WAN port connected to an ISP, a LAN port connected to the LAN, and then a third port (called what?) connected to the CPE which will act as both a LAN and a WAN port simultaneously somehow.

Am I insane?

Thanks,
Zaphod