You have infinite money, how do you make unbeatable tanks?

I think it’s a reference to the plate launched as a side effect of Operation Plumbbob. The detonation of the nuclear device launched the metal plate upwards at a ludicrous speed.

So if we’re recreating the WWII tank destroyer/assault gun, why not arm it with something crazy like a railgun or 145mm gun firing APFSDS rounds?

The thing would have to be enormous to use either of those…making it a hell of a big target.