Precisely my train of thought. Don't see why we need something so obtuse when an obvious, widely recognisable and - as far as I know - an otherwise unused symbol is available.

Plus, aside from the appropriateness of the symbol, it also conveys the digital element of the currency - it'd be more "on brand" if I was in marketing!

I think that the lowercase phi as a lower denomination is an excellent extension of the idea.

Other benefits are that it will get confused with the usual radius symbol (because it's exactly the same), and may be used to name an angle.

If I end up being able to purchase things with angles, I would not complain! Measuring angles with Bitcoins may be less desirable though ;)