Generic Error handler to deal with External Task service client errors

I am using External Task service client to perform some external task. During task execution it may run into some errors, eg. external service is down or an http 500 error.
Another error case would be to run task quota check for that user. If user exceeds his/her allocated quota then Error handler should handle it as well.
For some cases, re-try mechanism will be needed.
I have modeled a process using Event Sub-Process and Call Activity. Where Event sub-process is being used as generic error handler.

My problem here is, I want the error handling part to be totally independent of main process flow. It should have the capability to be updated independently of the main process. What I have modeled so far is still needs to be tied to the main process which makes it difficult to update it separately.
I also want a robust Re-try mechanism in my process but not sure whether to handle that in external task client or in bpmn process.
Does there exist more elegant way to do this ?

Thanks in advance for reading this and for your inputs!

I am also facing a similar issue. Are you able to resolve it.

No luck yet. I am still relying on embedding the Error Handling mechanism in the process itself. Hope someone from Camunda finds my question and reply