The 45 was a big departure from other Diana's of the period and is very well designed and engineered as you rightly say, Dave. The 34 countered with a simple but effective design that makes good power. I've always thought a polyurethane piston sealed Original 45, resprung to suit, would edge the 34. As it stands, I think there's little or nothing in it.
I like the stock, particularly the earlier version. The butt is not markedly lower than other models with raised combs and I think the gun handles nicely. Perhaps it's not quite as handy as a 34 or 35 admittedly.
Its worth mentioning that Diana brought out a later 45 based on the 34 so presumably the model was missed by some.
Yes, if it was re-released, all syntheticed up, I would definitely buy one. It would be a costly rifle though, considering it's relative complexity. That's what killed it in the first place.