Adopt Cluster / Machine API Spec
To not be marginalised and outrun eventually, we should actively engage with the community and eventually adopt the cluster / machine API spec. See gardener/gardener#231.
We have started and intensified the activities roughly 2 months ago and the team has achieved: https://github.com/kubernetes-sigs/cluster-api#api-adoption:
Following are the implementations managed by third-parties adopting the standard cluster-api and/or machine-api being developed here: machine-controller-manager
We are the first (and so far only ones). :-)
There is a very old branch of MCM that attempts to do this - https://github.com/gardener/machine-controller-manager/tree/cluster-api.
Here's a convo from the last year. @vlerenc sheds some light on the issue.

https://kubernetes.slack.com/archives/CB57N0BFG/p1573835150176400