We're looking at it all wrong.
The cap is for OTHER people to see!
We need caps that say things like "Ask me about my battery" or "IT'S NOT SMOKE!"
Well, what I do when people start coughing and hacking around me while I'm blithly vaping away is say... "what? Are you allergic to Elderberry juice? That's all I'm vaping to prevent colds..., I'm improving the air
My experience has been that people stop coughing immediately and go on about their business without another complaint, seriously.
And actual scientific studies bears out that there is NO SECOND HAND SMOKE (there is NO combustion taking place anyway, but there's no residue in the air EITHER):
http://publichealth.drexel.edu/~/media/Files/publichealth/ms08.pdf
I don't see why some vapers are willing to become martyrs and pariahs to hypochondriacs.