Vettel did not stick with Redbull , it Redbull that has stuck with vettel , he was a nobody two years back , if redbull wasnt designed by Adrain Newey he would have still been a nobody. Look up Adrian Newey's record , all his cars have won championships even with average drivers like Hill in 96 & Villeneuve in 1997 , then as soon as he joined Mclaren in the end of 97 Mclaren turned from Force INdia level team in 97 to champions in 98 & 99, you dont need good drivers when you have newey.
You say - a team without a bad driver cannot make a winning car. this is the sole reason why mercedes has schumacher working for them. they are not looking for short term gains. they know the feedback from schumi would help them in developing a strong car for the future. he made ferrari what it is today though they have been struggling for the last couple of years.
Micheal Schumacher is in Mercedes purely for commercial reasons because of his brand value , why couldnt ferrari make a good car from 1996 to 1999 for 4 years with him? Ferrari 's success was due to having great designers like rory bryne not due to schumaker .
as for vettel... and he would probably get a seat in ferrari the day he shows an interest. but he has not shown any interest until now because he knows that this is not the time to leave a winning combination and move to ferrari which is basically something you do when you have accomplished a lot and are looking for a retirement seat.
Of course it would be foolish to leave a team thats winning like Redbull but when did Alonso move from a dominating team to slower team for money like you said earlier, If Alonso is a douche then schumaker is miles ahead of him in douchery that doesnt make him any less of a driver ,
It was hamilton & his god father Ron who did not get along with Alonso, he learned to speak Italian & has long term contract with ferrari , there is a very good chance of Newey joining ferrai in future then we will see who is who.