That seems like the best option. Adding a motor to a longboard is just enhancing a known proven quantity. It won't have the maneuverability of a onewheel or the all-terrain ability, but longboards are definitely a proven vehicle for roadways so motorized ones seem fine.

Maybe there's some variation of the kickscooter that can meet the portability and compactness of a onewheel. Something that focuses on the foldability of the old Razor scooters. But that still wouldn't be as convenient.

Fundamentally, the onewheel seems like a personal-mobility answer to the V22 Osprey: a vehicle with amazing functionality and versatility in its happy path, but is fundamentally unsafe in failure because of the basic physics of the situation.

edit: onewheel, not longboard, in the final paragraph.

Some of the arguments made were about bringing the scooter inside a restaurant.

You stay in a restaurant one or two hours at most, and you simply wouldn't go there by bike if it's raining. It's unlikely to suffer from rust.

Likewise theft only tends to happen when a bike is left in the same location for extended periods of time. Defeating a good bike lock takes a special kind of people and tools, and your bike is unlikely to be spotted then stolen in a hour or two. One solution is also to park it in a relatively discreet location, or you could go for an area full of bikes (double-edged sword; more bikes means it's lost in the sea, but also that it's a prime location for thieves. Then again if you have a functional metropolitan police they'd be watching such locations).

Personally I use an e-bike in London, I attach it everywhere outside, I never had a problem despite my bike being very cool-looking (it's a British equivalent to Super73). While London is certainly more civilized than New York City, it does have significant crime as well in certain areas.