My personal favourite from your suggestions is the M113A2. It is probably the most 9.3 SPAA I have ever seen: often used chassis, no guns, only 6, kineticly defeatable missles which allow it to be 9.3, Radar (and maybe Thermals?).
It would fit really well into the 9.3 area. Do you know what radar it uses?
I want his thing in the game and add it to my 9.3 lineup hehe :)
What will be the criteria for a 6.3 spaa?
Based on Gaijin br.
20-30mm gun.
Decently mobile
Decently armoured
Fast shells with small drop
With AT capabilities
The thing I dislike about the Skink for the 6.0 to 8.0 region is its poor tracking. Doesnt feel like it can actually keep up with a fast jet bombing past.