BetaMod is designed to add units and abilities locked away inside of the Zero Hour files and to include new ones for a more interesting gameplay experience without taking anything away that makes Hero Hour what it is. If you want to add any media, that's fine by me, just make sure it's appropriate!
Even though the Mammoth tank has 100 less points of health than an Overlord, it is still able to take on one and win, but has so little health afterwards that it must return for repairs. A perfect moment for the enemy to strike.