A blower sticking up through the hood, isn’t legal in most states either. I have been working on a blown V6 Alpine, that when it’s done, will end up being just a race car or show car. It won’t be legal in California, where the owner lives. The forward vision is restricted, so most states made them ilegal.
Nitrous isn’t that bad and can be set up to come in in stages, with a small shot coming in first, then as you want it, the next stage can come in. I have had turbos and bolwers on my cars, but if I were to do another car now, I would go with nitrous.
As far as being illegal, only some states have outlawed nitrous. Nitrous is relatively inexpensive, and if set up professionally, can be very safe.