That's going too far. Carpet would produce ace-fests, which almost nobody wants. Although a couple of 250s or even 1 500 would be fine IMO, but not a 1000, and definately not ALL indoor events.
4th clay 1000? No thanks.
Carpet doesn't have to been lightning fast. The speed of the surface depends on the thickness of the mat laid on the cement. The thinner the mat, the faster the carpet, but also the more dangerous it is for the players' ankles. So by using slightly thicker mat, the carpet would be fast but not too fast, and safer than an indoor hard court. In the past I've played on slightly slower carpet.
And green clay is a distinctly different surface to both red clay and hard courts. Attacking players can and have always done well on green clay in the past, as well as clay court specialists. The US Open was held on green clay from 1975-1977 and Connors reached the final every year, plus there were numerous good quality tournaments like Forest Hills, Boston and Indianapolis on it that the likes of McEnroe played well at.
One big tournament on green clay would increase surface variety and be a nice change from too many hard court tournaments, especially too many slow hard court events. Green clay is a very common surface in Florida and Southeast USA. The tournament directors at Miami were close to changing surface to it about 10 years back. Green clay is easier on the players' joints than hard courts as well.