To put it simply. Make the Rift S (which is tethered to a PC) actually worth it. The Quest although a marvel in its self has ultimately destroyed the Rift S in terms of features, which isnt really that fair seeing as they were months apart from release meaning the Rift S could have easily had some of the same features as the Quest. What feature you may be asking? Simple.

-Manual IPD adjustment
-The 1440 x 1600 OLED display
-The up and coming hand tracking

And another feature which could easily be implimented

-90hz (or above) refresh rate (We know its possible just let us have it)

These features would make the Rift S actually entising for those who already have a PC and dont need a stand alone VR headset or people who dont want to sacrifice graphics quality.
Seeing as the two headests were so closely released I believe that these features should have already been on the Rift S. It would really allow the Rift S be something to consider when getting a VR headset.