I know that wii u gamepad works with 5 ghz but with many devices with 5ghz the connection is unstable so i want question you if it's possible replace the 5 ghz chips and use the 6 ghz chips?

Some times I play without issues and other times there is lag or it appears the writing connection issues. I already replacedWould require changing the chip on both Wii U and the gamepad. Would require firmware changes on both to work with the 6Ghz chipset.
So very difficult. Is this an issue you're actively experiencing? You're certain it's not a hardware fault (like bad connection to antenna).
I live in an area with a lot of radio, including tons in the 5ghz wifi bands. And never have connectivity issues. It's probably technically worse than it was day 1 when there was a lot less 5Ghz, but it still has no issues, and range is functionally uneffected for me.