Theoretical knowledge, language proficiency, medical requirements, flight training and testing should be proportionate for a rating which would require 600ft cloudbase and 1800m visibility for take-off, landing and at an alternate with approach minima no lower than 'IR minima' +200ft for precision and +250ft for non-precision approaches.
The problem is that your "restricted privileges" don't reflect the "restricted course" that you're proposing. They're arbitrary. The way weather works doesn't change in the last 200 ft of an ILS. Nor do the failure modes of your instruments. Nor does the the need to understand instrument procedures and work with ATC. Nor does the controller speak a different language. Nor do the medical demands on the pilot.
If you're saying that you can turn out some pretty good instrument pilots in 15 hours of IF training, I'd agree. You can turn out some pretty respectable VFR pilots in 15 hours of ab initio training too. But we don't, and we shouldn't, based on their ability to do a first solo circuit in CAVOK, give them a "restricted privileges" PPL which allows them to go and do the hardest things that VFR pilots have to go and do, as long as they stick to the arbitrary restriction of flying only on days with an 'r' in them.
If you can do the things that an instrument pilot needs to be able to do, to the standards an instrument pilot needs to be able to do to stay alive, you should have an IR. The best thing that FCL.008 can do for us is push for a competence-based approach to instrument flying and the IR, not an arbitrary second-class Susan.