I would approach your reporting as setting up a wan link group comprised of the 2 interfaces with a rollup method of show best status - this way the group will show fully available until both go down. (In practice I have had just as much luck with the default show mixed status and that provides better reporting of UP, WARNING, DOWN, etc)
You can then build dependencies just fine since once both links are down it will suppress all child devices (devices unreachable by Orion since the WAN links are down)
For reporting your standard group availability resources and reports would work just fine.
You could even build the groups dynamically by adding a custom property to interfaces like "WAN_LINK" yes/no then build your groups by adding dynamic query for Interfaces with SITE = "site name" + WAN_LINK = yes. Easy peasy.
Custom Query SWQL:
SELECT
n.caption as Node
, n.DetailsUrl AS [_LinkFor_Node]
, '/Orion/images/StatusIcons/Small-' + n.StatusLED AS [_IconFor_Node]
, n.Contact
, n.location
FROM Orion.Nodes n
left join Orion.ContainerMembers c on c.MemberPrimaryID = n.nodeid
where c.MemberPrimaryID is NULL