Discovery using value of tags for current instance

[marksmithson]

It would be very useful to be able to configure a cluster by selecting other instances based on the value of tag set on the current instance. This would allow an AMI to be created which will join a cluster based on the value set for a tag on the instance.

I am thinking of something like this:
discovery.ec2.tag.escluster: "{instance-value}"

{instance-value} would be replaced by the value of the escluster tag on the instance that the AMI is running on.

Is this worth pursuing or is there another way to do this? An alternative may be AWS instance data with cloud-init, but I have found this tricky to setup