I agree... and fair credit where it's due, you can't even get late Republicans in any variety in 28mm. Right now I'm actually considering just going for 20mm full stop... my few 28's can go onto E-Bay to fund my Minairons purchases.
It helps that I'm aware that Lluís is keen on the period (and afaik 20mm as a scale) anyway, so short of them not selling, he is likely to be committed to producing as full a range as possible. With the array of plastic and other kits considered too, it's likely that 20mm will offer the most complete 'experience' for gaming the SCW.