"What's the difference between a Service Request and a Standard Change" is a like the grey area painted inside a grey area when you're wearing grey shades on a cloudy rainy day.  I just chalk it up as two LANGUAGE paths to the same net effect:   "Something who's nature we know and we can repeat over and over with great confidence"

I would say do one OR the other but not both, as the second ticket bureaucracy buys you absolutely nothing.

So now you're left with "We already know how to request, approve, execute and report group/role changes.  Its already in place.  So what justifies the effort of rebuilding that from scratch"?