We do it a little differently - and for a different reason, being an ISP. We use 2 routers (ER-Pros in this case) with multiple carriers connecting to each one - we have the upstream carrier connect to us with a /29 so we have 5 IPs to use on up to 5 routers (we actually have 4 in operation right now - two old ones and two new ones that are replacing them) and we route all the traffic using BGP and OSPF through one router only. The second (and other) routers are effectively there for redundancy - you can use VRRP or something else to switch from one to the other automatically, or even use one for inbound and the other for outbound traffic if you want, or even spread the load across them if you really want to go nuts...
We find modern hardware so reliable that it almost never fails, and it's a bit more efficient to have a single router handle all the upstream connections. You could also use two separate routers (like your diagram shows) and have them talk BGP to each other, but that adds more complexity to the BGP config. The ER-Pros are plenty powerful enough for the Gig-E connections we use today, and in the near future 10Gig routers will be available to handle more when we need it.
Jim