Are you talking about the quick release lever so you can let people in the back seats easier? (similar to what the E4 seats have)
If so, im not going to say its impossible but its pretty damn close.
The E5/6 seats are only controlled by a crank system (crank the knob to adjust the back rest) and would require epic modification to add a latch, cable and lever and doing that would surely breach some ADR policy.
there is a way, but its custom DIY, tutorial is on Evo forums from memory ask EVL.20T he linked me to it ages ago and he might still remember where the thread is