Tbh I think it will favor wrestlers a lot.
Using the cage is the safest option for strikers defending takedowns.
With grounded knees allowed, I think fighters would be too Much concerned in not eating a knee in his face, and probably worsen a lot their TDD.
Ok, now wrestlers will have an additionall weapon, and a worth of highlights one.
But how I pointed before, I think the defensor will be too much concerned in not eating a knee, and probably we'll see more fighters given away the takedown.
I think fakeing a knee then drive the opponent to the ground will be their new staple.
wrestlers can already being kneed in his TD entrance's, but I dont think is very smart trying to knee a guy already clipped to your legs, you can't generate much power and will probably just eat a single leg.