Looking at several old classic path racers and more recent homages like the Pashley Guv'nor, many appeared to have been fitted with upright handlebars that were merely flip-flopped for a lower profile. But most had back-turned bars. Mine aren't quite straight but not turned back much, so the wrist position may be the limiting factor.
We're due for t-storms all week, so I'll have time to piddle around with the existing handlebars to see if flip-flopping the handlebar is useful.
"Check for knee - elbow/hand clearance on tight turns."
Yup, I video recorded myself riding this weekend to get an objective look at my riding position. The main hindrance on tight turns is toe overlap, but this only happens at slow speeds on tight turns, and it always gently nudges my foot out of the way so no harm done.
Looking at the video -- taken on a very windy day -- I might be able to get by just pivoting the bars forward a bit. I noticed my arms are bent at the elbows a bit more than necessary, with my shoulder blades hunched together, when I'm trying to tuck in while riding against the wind. I could probably improve on that a bit just by repositioning the bars.