This is a picture from the Zev Technologies website. It features a Glock 34 length barrel & slide on a gen. 3 G19 frame. This in 357 Sig would be an interesting weapon. Especially with a red dot and downrange cartridge performance.
I put a 357 Sig barrel in a G35.
Bar-Sto is also making Gen 5 357 Sig barrels for the G22, I’ll bet they would easily sell a longer one that could fit a G35.
Then you could use a G19 Gen 5 frame.
IMO, a G19 frame with magwell is about the same length as a G17 grip so not sure that I understand that construction design.