Thanks for the thoughts.
This is kind of the value calculus I was running in my head, with the “downgrade” comments being driven more by the considerations of RAM and processor power. The Mini 5 has significantly less of each, and that’s the sort of thing that I think affects long-term usability more than anything else.
And the other thing that irritates me a little bit is the on-screen keyboard for the non-pro vs. the pro iPads. The “pro” has a much better on-screen keyboard (including the swiping on a key to give the capitalized version), but doesn’t allow a split keyboard. Whereas the non-pro allows the split, but lacks the other features.
I’d be ecstatic if Apple made the keyboard on the non-pro work the same as the pro models.
But yes - the ergonomic considerations are paramount. Since I posted this I found a friend who was willing to buy my Pro for enough money to let me get a brand new Mini 5 with 256 GB, Pencil, and case.
I’m using the Mini 5, and I’m pretty happy overall. I’m learning to two-thumb with the split keyboard since the iPad actually fits in my hands. 
Even if it’s a little bit less “power” than I’m used to, at least it’s got a relatively current processor, plenty of storage, and a fresh battery that will last several years. 
I considered that, and that’s one of the reasons I’m discussing it now after the spring iPad event rather than when I was thinking about it originally back in February. 
That said, the rumors are also swirling that the iPad Mini might increase in size - and even with a spec bump, an increase in size is exactly what I don’t want. So if a new one drops in the fall (I can’t see a summer release) and it’s the exact same size, I’ll have been wrong. If it’s a bigger size, I’ll almost certainly have made the right choice by getting the smaller one now.
Either way, I’ll have 5 months of actual use of the iPad since it works so much better for me than the 11". 