P: Transform/Resize is constrained by default - Want ability to go back to legacy behavior

Oh, I sympathize. I think someone is asleep at the wheel at Adobe.

Just press Ctrl+T(Windows) / Command+T(Mac-Os)
then right click and select Distort.
Done!
Enjoy!

Jeffrey, this is not good enough. It's been many months since the free transform fiasco began, and you still haven't addressed one of the most glaring (and oft-complained about) problems: inconsistent transform behaviour between layer types. If you're going to ill-advisedly fool around with the default free transform behaviour then so be it, but for God's sake, finish the job!

With "Use Legacy Free Transform" unchecked, shift constrains vector layers, while it unconstrains raster, smart object, and text layers. Not to mention that Photoshop's default behaviour is now largely contrary to the behaviour in Illustrator, After Effects etc. This is poor interface design no matter how you slice it.

It adds insult to injury to refer to the previous (sensible, consistent) behaviour as "legacy" when the new feature remains unfinished, inconsistent and illogical. At the very least, the new behaviour should be called "beta" or "experimental" (and turned off by default) until you finally finish implementing it. 

I'm sure it's very tempting to write off the deluge of criticism you've received over this issue as just being the white noise of the angry internet masses. But honestly, Adobe dropped the ball on this one, and made some objectively and glaringly obvious poor decisions, the solutions to which are likewise glaringly obvious. 

Spending 8 months to add a legacy checkbox smacks of 'throw the complainers a bone to shut them up'. It signals that whoever's in charge of things over there hasn't actually listened to the customers, or genuinely comprehended what Adobe's mistakes were.

Bring back Proportional scale in Photoshop.

Why are they insisting on plinking around with WELL ESTABLISHED TOOLS? I use 10 image editing applications everyday. Do I really have to learn a new set of trick for a program I have owned since 1991??

Jeffrey, the team at Adobe really need to do a better job notifying customers of changes like this.

We expect better than to have to exit the software we pay to use, to search online for answers.

We should not need to look into patch notes or forum posts to find out why one of the single most-used tools in all of Photoshop has changed behaviour after 15+ years.

Adobe's rinky-dink approach to customer experience is tiresome.

I found a new "Show Reference Point" tick-box in the Options window/palette!
I guess this was another newer addition that came disabled...
It allows you to see the old reference point target, move it around, then scale to achieve the outcome your diagram describes. The mid-point handles remain limited in use and "Constrain" does not effect them.

October 2018: https://forums.adobe.com/thread/2550466

Found a new "Show Reference Point" tick-box in the Options window/palette!
I guess this was another newer addition that came disabled...

After 20.0.5 the constrain behaviour does not work on the mid-point handles.
How long has the ability to move the scale centre point been missing? That's a big omission IMHO. Especially when I want to constrained-scale from an edge centre point.