They had a 40mm watch out years ago and I tried it. I didn't notice a comfort improvement over the regular sized PAMs that were 42 & 44. Also, I don't think I would purchase what might be considered a "Mid sized" PAM, as if I ever got tired of it and wanted to sell/trade it, its smaller size would probably reduce its resale value and/or reduce the ease of finding another buyer. I really like the design of the Luminor but I think its just not a watch for me.
the 40mm panerais arent worth getting into. I knew far too many guys that were leery on the 44mm size so they bought the 40mm, and after getting used to the size, really wishing they had bought a 44mm and selling the 40 at a huge loss to fund a full size. Years ago when i was heavily into panerais and buying/selling a ton, i bought my wife a PAM49 (40mm) she still has it, never wears it though. I replaced the pink gator strap and put it on a standard brown calf so i can wear it. Its boring. If youre going to get into panerais, it kinda has to be 44mm. If its not for you, its not for you. Thankfully, theres PLENTY of other watches out there