Wouldn't F1 as a spec series be very dangerous? I mean the reaction times are already very short, the sport is open-wheel and contact is catastrophic.
What's dangerous about a spec-series? Spec-series means all of the cars are exactly the same
specification, it doesn't mean the cars are super fast.
GP2 is a spec-series, Formula 2 is a spec-series, Indycar is currently a de facto spec-series. None of these are any more or less dangerous than Formula 1 is.
A Spec series would be great as it would show who truly are the best drivers rather than who has the best car but what would be in it for the teams? It would be an end to the constant development of cars which is one of the high points of F1 today.
It wouldn't necessarily show who the best drivers are though, because a specific car can only suit some drivers and not others. Look at Kamui Kobayashi, he looked like nothing in a spec series, but with a car more tailored to his style, he comes alive. I also don't buy into the "the best drivers are most adaptable" - even Lewis Hamilton is disadvantaged with a car that doesn't suit him, just because he is more able to drive around that, doesn't mean he isn't disadvantaged and isn't visible to us.
Then you have drivers who sit in series for several years gaining masses of experience before winning during a season when there are more rookies (e.g. Pastor Maldonado, Giorgio Pantano, etc).
Plus the fact that just because each driver has the same car, doesn't mean they have equal chances. A driver who is at a top GP2 team like ART or iSport will benefit from the best mechanics and engineers, who help him setup the car better or provide faster pit stops and better strategies.
The plus part of a non-spec series like Formula 1 is that the team can develop the car to better suit the driver's style, which is far easier than simply changing setups.
For the most part, GP2 champions are some of the best drivers out there..but then the same can be said for F1. Someone that is a backmarker or midfield driver in GP2 barely gets noticed. Someone who manages to drag their backmarker car to a 10th place finish gets noticed, partly because F1 is more popular but also because we appreciate that the driver was driving an inferior car - we can appreciate the achievement better.