I say allow everybody to invest. Currently ICOs allow everybody to invest and everybody like them.
Careless impatient stupid newbies will eventually waste their savings, go broke and stop investing in ICOs at least because they will have nothing to invest at some point. So eventually they won't need protections anyway.
Smart, careful and patient people will make money.

Trying to create a system that protects careless impatient stupid newbies makes it suitable only for those and unsuitable for smart careful people.

So we already have freedom of choice - IPOs and official stock market - for stupid people and ICOs and crypto for smart people. We should keep it that way and make ICOs legal with the way they are conducted now. Mere legalization without changing anything will reduce amount of scam, see my thoughts here: https://steemit.com/securities/@alpav/securities-laws-are-only-helping-scams