I don't know what makes you think there would be a problem.
When you have 2 routers you actually need 2 vPCs, connecting each Nexus to each router
R1 R2
(| \) (/ |) => vPC1 connecting R1 to N1&N2
| \ / | => vPC2 connecting R2 to N1&N2
| X |
| / \ |
| / \|
N1=====N2
Logically this is nothing different than that:
R1 R2
(||) (||)
NEXUS
Now the server connected to the Nexus switches arps for the Gateway MAC and receives one virtual MAC-Adress from the AVG Router.
I'm not sure if this does answer your question though.