I drilled out my nemi back in 2013, thought the same thing as you. I took it to an actual brick and mortar Vape Shop here in Southern California and had them use their dremmel (usually used for drilling out atty caps) and expanded the battery exhaust to 1/8 size. It helps. BIG TIME.
I only dual and sub-ohm, so now all the mods I own have a pretty decent battery vents anyways, and admittedly my nemi has gotten replaced by a lot of my newer mods that hit much harder. Was thinking about getting the newer "matte" nemi, that thing looks sexy. One thing I never liked about my Nemi was the locking ring, the switch at the bottom would get stuck from heavy, heavy use. It was my daily weapon for at least half a year.
Now I'm a fan of the mods that don't have locking rings, and you can set on a desk and not have to worry about it firing, The Cartel Mod is a good example of this switch design.
To your original question, you can drill it, I wouldn't recommend doing it with literally a "drill" I'd use a dremmel, and I'd take it somewhere that normally charges people to drill out their atties, most likely they'll make you sign a waiver in case they .... it up.
