I found a minor "use": Wallace has a great "aggro", all monsters go to pursuit him...so it can be used for a partial "manipulation" of the tactical combat.
Anyway, I use him only in the first combat where he usually dies. If autoresolve do not finishes him, then he WILL die in the second fight.
If he could be "henched" (grow levels and get traits, maybe even giving him items) then maybe he could be an interesting character to try to keep alive.