There are a couple of guys on a FB group I'm in that have velomobiles, and they have quite a few incidents with law enforcement. One guy I know of has been pulled over something like 40 times in his velomobile because they all think it has a motor and want to know why it doesn't have a license plate.
If you're in an area where the cops don't respect cyclists much, you'll likely have a LOT of problems in a velomobile.