fluxCD brings a really nice helm-controller that will allow to change manifests via a postRenderers stub while still allowing to use regular helm tooling against the cluster.
Yeah, but then it is yet another layer of configuration slapped on top of the previous layer of configuration. That can't be the best solution, can it? Same thing for piping helm template through Kustomize.
Yeah, this setup is both nice and insane. If you don't need much extra customization it's great. But I have a setup where I needed both postBuild and postRenderer's + actual kustomization layering and it was awful trying to figure out the order of execution to get the right final output.
In hindsight it would have been much faster to write the resources myself.