Im from beta and i cannot remember your so called balance issue. The only light vehicles that existed was the m3 and nothing else because of the callin meta. you didn't use shreks to counter the m3 especially since the m3 was usually the rather common sniper+m3 combo and could nail your shrek squad with simple kiting.
i thought that the double shrek upgrade was added for easy use.
Because it happened in alpha.
It was long fixed by beta.