[yunwal]

Requirements imo, should be 1) All used words are guessable 2) There are no possible alternate solutions with unguessable words

I haven't done the math, but I suspect there are plenty of solutions like this, you'll just have to calculate them.

[jimmydorry]

It would probably make the difficulty guide inaccurate, unless you take the lowest possible difficulty as the guide where ever there is more than one solution.