I really can't figure out why I've been lucky. I had to drop my Cuboid a bunch of times before it wouldn't do TC. I've dropped many others, although not as much, the Cuboid was a daily vaper for years. I've had plenty of liquids leaked inside of every mod, over every button. Only the Cuboid and RN4072 auto-batts back to 2009 don't work as like new. I have had to take some apart to clean/dry.
I think you all are doing something wrong.
You could plug the vent holes with something like wax. It can be water tight and still be a place for pressure to vent. I know some will say no you can't cover holes, but I know guns and they rely on pressure from an explosive force going the way of least resistance.
I'm amazed you can find mechs without vent holes, that's a pretty standard safety thing. The lack turns flame and gas into boom.
I checked, IVP Mini II is about 5mm length and width less than Proton, but a bit taller. Where did you put cigarette packs? Proton should fit anywhere a pack fits. That's what works for me with boxes. Before with stick mods I'd sew up the center of cigarette pockets to hold 2 mods without banging together. Even my VTR (old Itaste box, weighs about 20lbs) fits in cigarette pockets. I even fit boxes in my screwdriver pockets on my bibs. Everyone should wear bib overalls.
Ego batteries was about size. After 18650's I'm not seeing the size difference. My mech is bigger diameter than my 18650 regulated sticks. They may not be able to sub-Ω but that's more an issue with their time in history.
So other than portability in your tiny pockets
what about how the Proton performs in either VW or Bypass compared to a mech?
That's my first thing, figuring out portability comes after, except drippers, I never could figure out how to go from here to there without spilling a dripper all over. TC & squonking fixed everything but that.
I never could get mech vaping to be something I wanted to take with me.