I think you would need the small-scale "gashapon" or "shokugan" figures to proxy the smaller Tau suits. The former come in blind-buy capsules dispensed by a machine. The latter are sometimes blind-buy, come in conventional box and include some chewing gum. There are several different serieses, such as
Senshi Forte,
Converge and
Ensemble. The problem with these is that they are not on sale for very long before being rotated out for the next item in the series.
Mobile Suit Ensemble figures are probably the least super-deformed in their proportions, and they are little kits rather than figurines. There is also the
G-Frame series. These are properly-proportioned but basic kits, but they may be approaching
HG kit size, i.e. 1:144 scale.
What would have really suited your purpose is Volume 1 of the
Gashapla range, which were all Zaku II mobile suits. Unfortunately they are
OOP, but for reference you can see an example of the full range
here and my build of one
here.