Well they already can in exactly the same fashion that we already see weaker armies win. The other guy has his retreat settings set lower than you do which quickly rights an imbalance. Calvary can be used effectively against unprepared infantry formations.
Digging in may actually be incredibly useful again as when a flank falls is incredibly important. The sudden influx of troops to the middle plays absolute havoc on the other side. If you look at turn 2 you can see that the eventual loser actually was ahead at one point. If that kept up for another turn they would've done incredibly well.
