Yepez played outfield in St L.
If you split 1st and DH among 3 players, and figure a backup infielder for 2d/SS/3d, plus a backup catcher, that's 3 of your 4 bench spots. With Crews and Wood capable of playing CF, you have a bit of flexibility in that last spot provided you are comfortable with one of those guys in an outfield corner. Alternatively, there's Call.
Whether or not AZ picks up the option on Suarez, the Nats need an ace starting pitcher more than a hitter.
I don't think "just sign Joc and go with the internal players" is how you build a wild card roster, unless you spend on a true ace (plus just a little on bullpen depth). That lineup could be around .500, and any plus side puts you in the WC mix.