If you suspect windshear may be encountered, you may delay rotation until this higher speed, but V2 is calculated and set in the MCP normally.
That sounds pretty sensible to me .. but, in the event of windshear, it follows that you disregard the bugged V2 and go for the indications on the ball ?
Similarly, if you don't have windshear, you are not going to reduce to the bugged V2 but, rather, keep whatever you end up with up to a sensible overspeed margin ? With the OEI caveat relating to very close in obstacles, to reduce speed would be a tad silly, I think.
If you encounter windshear you fly the windshear escape maneouvre, which is based on attitude and stick-shaker,not IAS.
Tarket IAS for a normal take-off is V2+15-V2+25, so the extra "OOMPH" will probably just leave you at the upper end on that.