Why can't you achieve the equilibrium exactly in the middle (K=1) when you add enough heat/energy?
There are indeed reactions where the equilibrium constant passes through unity as a function of temperature.  The water-gas shift reaction 

$\ce{CO + H2O &lt;=&gt; CO2 + H2}$

has an equilibrium constant that gradually decreases with increasing temperature (it's slightly exothermic as written), and the constant is close to $1$ at $\pu{800°C}$.