I'm not fully sure what you're asking for here exactly... you're going to need a v4 infrastructure to route v4 packets, because that's what having a v4 infrastructure means.
You can map the entire v4 space into a v6 /96 with NAT64. That works fine, giving the same sort of outbound-only connectivity that NAT gives in v4. Does that do the job?
You can map the entire v4 space into a v6 /96 with NAT64. That works fine, giving the same sort of outbound-only connectivity that NAT gives in v4. Does that do the job?