Do you have a write-up about this that you have to share, even if it's someone else's? I'd be curious to try this out.
I have an infrastructure layer that I apply to all clusters that includes things like cert-manager, an ingress controller and associated secrets. This is all cluster-independent stuff. Then some cluster-dependent stuff like storage controllers etc. I use flux to keep this stuff under version control and automatically reconciled.
From there you just deploy your app with standard manifests or however you want to do it (helm, kubectl, flux, whatever).
It all works wonderfully. The one downside is all the various controllers do eat up a fair amount of CPU cycles and memory. But it's not too bad.