Interesting idea gi-minni
Have you also looked at VMware NSX?
what do you think your solution would bring to the table over integrating the router/firewall directly into the Hypervisor level?
maybe you could also look at using pfSense + the vmware API for layer 3+ features from pfSense and turn pfSense into a awesome competitor for the juniper and arista networks gear.
most of the NSX is based on Nicira's Open vSwitch so here's hoping for compatibility :)