Maybe we should examine the whole topic from another angle. As Inverse stated Panthers are a rare occurrence in 1v1 games, as for 2v2s I've seen quite a few of them used by myself or my opponents.
One of the reasons why there are more tanks in team games is the abundance of fuel. It is the result of the pool of available manpower to build Observation Points (henceforth referred to as OPs) and the number of available strategic points.
There are two possible ways to address this.
1) Limit the amount of OPs that can be built by the team to a specific quantity, for example 2. I'd assume that this is rather easy to implement. (One could also remove the fuel income from not OPed strategic points)
2) Reduce the number of strategic points on the map, which would have the same effect as 1).
As for the possible repercussions of this, it is probable that there will be a greater reliance on infantry and their counters. Whether this is a change for better or worse will be in the eye of the beholder.
