OK, dropping in a bit late...
IMO HG minis are not only incredible beautiful and stylish they also work in multiple scales.
If you use them as Robots it is almost irrelevant if you are using them for 6mm or 32mm.
Only if you want to use them as "pilot is in the chest compartment" they are limited to certain scales.
And that goes for the current 1/144 (10/12mm) or old 1/87 RAFM (18-20mm) scales.
![](http://www.adpublishing.de/assets/images/HG_Crisis_sm.jpg)
Old RAFM Heavy Gear (Northern Guard Kodiak Destroyer HACS-10HG-TH) for size comparison next to a TAU Suit.
However please keep in mind that not Gears have the same size.
You basically have 3 size steps:
Small - Cheetah, Iguana - 24mm (curren tline)
Medium: Hunter, Jäger - 28mm
Big: Cobra, Grizzly - 32+mm