its a crap idea, if it was any good you would see this on all the super cars. people have been perfecting turbo set ups for years, and for very good reasons non of them have done that.
main problem would be the spool time, the engine has to pressurise the gas behind the turbo to a point where the turbo is fully spooled before decent boost can be made. with the turbo right next to the engine that is fairly quick, but with the engine having to pump the entire exhaust system full of gas before it reaches a decent pressure you will have changed gear by then... its just a crap idea.
having said that it does look kinda cool, something a little different.