Is it possible to establish a "default" route for IPv6 traffic that is different based on the interface the traffic comes in on?

Example:

I have an IPv6 tunnel from HE with a /48. I've created three different subnets on VLANs for isolated servers - call them Open, DMZ and Test. Up until recently I had a 4th subnet defined for the more general LAN. All four subnets are properly isolated using simple firewall rules.

Last week I activated Comcast's native V6 service. It works well and has better performance than the tunneled service. But for now I can only get a single /64 allocated from them.

I want to use Comcast for most IPv6 traffic. Right now I have the default route set to send traffic to them (ether1_gateway). I'd like to have a second "default" roiute, but only for IPv6 traffic originating on the virtual interfaces "Open", "DMZ" or "test" and have it route the traffic on the tunnel (sit1).

Should be the most simple of source-based routing scenarios. The IPv6 route configuration even seems to have options for it. Except that you can't use them.

Thanks in advance.

Nothing?

Bump.