Unfortunately EnginedUnitsScrappedChance=100 didn't seem to result in any scrapping.
I tested 2 of 3 possible scenarios:
- attacker wins, defender recovers own mechs (tested)
- attacker wins, attacker recovers all mechs (tested)
- defender wins, defender recovers own mechs (didn't test)
I didn't test gyro scrap chance, legged scrap chance or 'forced' scrap chance, but I assume the are broken as well.