Your ideas are pretty nice and could be done. Some of them already done:
* several cameras could be connected to virtual camera and showed at the same time or switched from one to another by model. It is easy to allow customer to switch between cam devices
* We have application allowing models to stream from mobile devices and receive tips or private chat directly at iOS/Android devices already but it is not really popular.
* We have developed first version of USB based vibrator about 7 years ago but was not able to use it. The same time chaturbate driven by small tips using it very well - it is mainly depends on user traffic
* Tipping model is already pretty easy
* Forum/Blog already available but who would read it?
* buy and send gifts is not what models are looking for - they need money.
But would be good to buy something personal from models (panties, etc)
* Models in WebVideo already visible on all webcam sites based on our platform
To draw the line - you need real traffic, real customers and based on real needs you can do something new and popular at the same time.