I think the spec-series choice is to give the series a good financial foundation before they start asking teams and manufacturers to start investing big. Who is going to invest in electronic racing if it turns out to be a massive dud.
Fanboost, makes sense. Motorsport is becoming so far from the minds of young people the series has to engage people in new ways. I don't 'like' it, but Formula E isn't going to be success if it tries to attract orthodox racing fans. There's just not enough about that will want to watch.
They do look slow though. I guess the FIA put in performance limits to make sure GP2, GP3, WSR etc... all remain relevant and viable. If Formula E started lapping close to them speeds suddenly you have a class that all the younguns want to spend daddies millions on.