Grossly, insanely different PD strengths

[NTJedi]

Lord_Bob said:
Another player even made a point of mentioning how bad Machaka PD is. So yes, quite, they are considered weak.

During DOM_2 I originally enjoyed Machaka, but the weakest PD is more noticeably painful on my favorite type of maps(LARGE). Today I still joke that Machaka PD can be killed with tennis balls.
One benefit of these discussions on PD has made me realize DOM_4 should allow gamers a way to upgrade the PD via one or more of the following research, gold/gems, new -/+scale, building type, etc. This would add another layer of depth for gamers.