I think double pumping, and anything beyond that, takes away from playing diversely. I remember a match in the first Halo Wars where this UNSC player had two bases with 4 vehicle depots and nothing more than supply pads. He pumped nothing but Scorpions the entire game.
Yes, because if you have the eco for it double/triple/quad pumping the same unit is a factor of the game. What you should do instead is scout out the enemy, see what unit recruiting they have and then counterbuild.
For example if you see someone double pumping scorps in Halo Wars 1, you see if they have two or three reactor levels, if they only have 3 you can…
Counter with Banshees (Covi)
Boom yourself to canister and fight fire with fire.
If you have teammates have one of them go maybe hunters, Cobras while are “anit-vehicle” lack the very thing they need to do so, mobility. Unless you have cobras enmasse which is impossible if they are boon eco scorpions then they will either get demolished or outmaneuvered.