msucymbal wrote:Let me ammend my post....20 'mm' for a base, not 20 'cm'.
Ahhh, that's what I expected you meant. 20mm is awfully small for a Lego minifig. 30mm is just under the size of 4x4 studs, and that's the best size to comfortably mount a fig facing forward with no overlap. It gives you some room for shields and weapons. 3 studs can be done but it gets really cramped especially if you use shields. But 3 studs is still more than 20mm. So, you are down to staggering the figs front to back or turning them sideways and have their head face forward. Either that or simply expand to a larger scale and only play Lego against Lego (which will look better anyway).
One of the things I was looking for in a set of miniature rules was the ability to reasonably handle Lego figs. Warhammer really doesn't do that.
What I would do is mount the figs on a 2x2 baseplate. Then I would use double-sided tape to attach that to a small flexible magnet (you can find them in strips or sometimes sheets - they can be cut to fit easily). Then you can attach the figs to a correct size metal movement plate (thin tin works). The magnet allows easy removal from the movement plate and you can position the figs as tight as possible.
Dunno about mounted figures, though. They take at least six studs in length, not counting any tail or head overhang. You don't mention base depth, but six studs is just over 45mm.