Although I do not really disagree I feel the need to correct some facts:
Puma does not have have high penetration:
Penetration near 160 Penetration mid 120 Penetration far 80
nor does is have good accuracy and it becomes good vs mediums only at mid range.
Puma has rather low armor and it can be damage by HMGs.
Imo Puma does not have a shock value but "counter shock" value since getting a Puma when you opponent has no vehicles will have little effect but it can counter many enemy vehicles.
AEC does not have bad penetration but rather inline with cost and ability with 1.000 penetration.
Penetration near 120 Penetration mid 100enetration far 80
Stuart can reckon since it get bonus sight as vet with a sight of 58.5
Luch also get bonus sight with sight of 45.5
Finally I would like to point that there is difference between having a good design and being balanced.
A unit can have great design but be UP or OP and units can have poor design but be balanced.