I think the pictures bring the problem with prone figures to light very well - the need for bases of an unusual size (ie. anything except your normal infantry base - whether it is 20 or 25mm and round of square). A pity as while my head says prone figures are good and realistic they just aren't as much fun.
The GW heavy weapons do look very big and awkward, just what I would not want to see from Wargames Factory. Maybe barrels that are rather more than 10% of the weapons total length as well! A pity as the GW Cadians are generally very nice figures - the ones to beat for Wargames Factory.