Problem with the snort mast dipping below a wave is you still have two big diesels sucking the subs air.
Must resist temptation to make joke about submariners getting a Seal stuck on their periscope.
Or even worse, a sealion.
What if, instead of sucking air out of the crew compartment, the engines used a compressed air tank? That way, snorkeling is bearable for the crew. Maybe not a solution for stormy weather, but if the storm is that bad then ASW aircraft might be grounded, so the U-boat can run on the surface.
The other problem is that snorkels couldn't be run above 6 knots because they might break off. This can just be fixed by reinforcing the snorkel. Sure, it will take a few design changes, but that's what engineers are for.
This way, boats can travel shallow at full speed, and switch to electric motors to go deep. As an added bonus, the KM might design a real underwater sub using the snorkel, instead of the primarily surface ships with some dive capabilities of OTL.