I think DRS is fine as it is, there are a good range of tracks on the calendar, each with their own strengths of DRS: some tracks it is very tough to pass even with DRS (Brazil, Japan) while other tracks multiple cars go through (Italy, Austria). These differences make the game more challenging to master and give you something unique to think about each race!
Also slipstream is literally just DRS but everywhere! Not sure if that's really what you guys want.
But having a single strong DRS really dictates how the game is played, while having several, but significantly lighter DRS zones would be really good for racing and would be long to learn all of them if you consider that you have several different DRS zones each race. Also slipstream would be fine, that's literally the "balance" for dirty air in real life. Instead of overtaking each other each and every lap, you'd see actual racing where you can follow the leader pretty well, but it would be harder to overtake.