Yep, i'll mostly agree with that Rod. I owned quite a few large capacity bikes in my younger days, but there was less traffic and regulation. Also, larger capacity bikes back then did not appear as physically imposing as comparable bikes today.
One of my smaller bikes remembered with great favour was a Honda CB 400 Four (blue). I loved this little bike for the vesatility that it offered; remembered as being a smaller unit than the current Honda 400/4, which is not a bad looking bike in a traditional naked bike way (I owned a 350 four also -green- but it was a feeble cousin compared to the 400).
I pulled up in the back of busy Bondi late one arvo last week on my Dio. When I returned, there was a Majesty 400 parked alongside. The Majesty looked like a bus next to the Dio and I thought for real metro work even this scooter had limitations.
Weight also becomes an issue - in congested situations - when you get older. I looked at the specs on the 2017 Burger 400, but kg weight was over 200. Sure the weight is down low, but that does not offer a compromise for every requirement. The 102kg of the Dio has me hooked on metro nibleness. My 69kg rider weight is a measurable factor.
Ideally I want a Vespa GTS 300FL. And that's where it all started for me (the FL wasn't available back then). Good for town and burbs duties and for the odd occasions I could get out of town, maybe a bit of credit card touring (but this assumes that I would keep the Dio also).
So my point is, like you Rod, I think a good 3-400cc machine, on well considered roads, is going to put you in the frame.