thanks
Not to my knowledge no but nothing stops anyone from developing one
Isn't actually or can't the NCC become an online wallet by
implementing client side signing?!
NXT for example is easier because it doesn't store the funds or addresses on a wallet file, instead, it's a brainwallet that is kept in the network itself. An NIS would need to safely store the data on a file, thus needing to sit on the server. Unless the online wallet site sports a SSL certificate, it could lead to funds being stolen (for example). Every private key is yours to keep, but even downloading / uploading those are a potential hazard.
You are right that the brainwallet has its own set of problems. For those who are interested, you can actually create a brainwallet out of the NCC and the NCC source codes are for your taking!
The good thing about the NCC design is that it actually provides the flexibility of implementing some kind of a brain wallet but do it at your own peril!