Is there an option to nominate No Tertiary Ability?
In short, I heavily believe that to create a stat spread that can support Weak Armour and Illusion well enough to believe choosing one ability over the other has Risk/Reward, but I honestly believe it would be nigh impossible to
A.) Choose an ability that meshes so well with Illusion and Weak Armour that there is risk/reward to choosing the third option over the other two.
B.) Create the rest of a Pokemon (stat spread, movepool, etc) around predetermined abilities that already need very specific support to work effectively.