Cloud formation and VPC's

CloudFormation with VPC's and VPN's.

Hardware VPN connections from our datacenter to our end points in the cloud.
VPC's are used on the cloud side because VPC's are awesome.

Everything is connected together such that we have a single VPC and multiple subnets that can all route on the VPN back to the bare metal resources.

I use tags on the VPC, Subnet, and NetworkACL objects to determine which resource to connect to.

What would be nice is a way to reference an existing resource by a search query objects.

For example:

{
  "Resources": {
    "ExistingVPC": {
      "Type": "AWS::EC2::VPC",
      "Search": {
        "Dimension": { "Tag": "primary" }
      }
    }
  }
}

I'm leaving quite a bit out here, but the basic idea is to have a search query to find an existing object.  Additionally you could also include the ability to include the "Properties" hash as a series of overrides.