Should you ever deploy your blank at a position other than an edge in Epigo?
Short answer: No.

Longer answer: Unless I was playing a variant, I would never consider placing my blank epigon anywhere other than on a board edge.  Having 2 sides that can be attacked at the start of the game seems like a bad way to start things off to me.  I am sure there are some variants where it would be acceptable to have your blank somewhere in the middle, but not for the base game.