I think the strategy is too much centered around running the two team cars togheter to get DRS every lap or catching a DRS train. This is what I observed in a high level racing and even in my races when leveling from 9 to 10 to 11 the DRS strategy is slowly becoming the dominant strategy. First the car need KERS to overtake, next level less KERS and then next level without KERS. The overtaking is at first with just a little bit and not very much time is gained because the second car is pushed back to some sort of minimum gap, then next level the overtake is a little bigger and the second car is pushed less and this way time is gained against cars/teams who dont use this strategy. In my opinion the race strategy is totaly centered around running the two cars togheter the whole race.
TL DR:
My recomendation is when using DRS against a car the power of the DRS aginst that car is reduced by 1 for the rest of the race. Example team has DRS 15 and is running the two cars togheter. In lap 3 car 1 is using DRS against his teammate car 2 to overtake. Now car 1 is leading and its DRS value against car 2 (his teammate) is 14 (15-1). In lap 4 car 2 is overtaking his teammate car 1 to take the lead back and after this the DRS against car 1 is 14 (15-1). Now in lap 5 car 1 is unsing DRS against car 2 to overtake but the power of DRS is now 14 because he already used DRS against this car and also his DRS against car 2 for the next DRS is reduced to 13 and so on. Later in the race car 1 is using DRS aginst some other car from other team lets say car 5.
The DRS against car 5 is 15 but after usige is 14. Later in the race car 1 is using DRS against car 5 and DRS power is 14. After this the DRS is reduced to 13 against that car.
Short: When a car is using a DRS against another car the power of DRS against that car is reduced by 1 for the rest of the race.
For shorter distances (50% 25%)maybe a larger DRS reduction since there are less laps.
I think the main result of such change will be reduction of the power of the DRS teammate strategy while it still will be vaible, but not as wholle race strategy and also some reduction of the effeciveness of DRS trains.
Also in general the result will be more possibility to run different strategy for the two team drivers.
In my opinion is also much easier to control two cars running togheter then two cars that are placed in different points of the track - just additional note.