It would be interesting to see the proposed new robe styles. If I recall correctly, in the Vinayamukha there are a series of images of different robes styles, perhaps it is in there.
I haven’t researched on whether it’s possible to infer robe sizes from Buddha images. Remember, they’re all many centuries after the Buddha, so could be a hint only.
As for the sugata measure, this is sheer speculation. No-one knows what it really was, but 25cm is certainly too small. There are several problems with the 25cm size, but one of the most severe is the size of the nuns’ bathing cloth. If I recall correctly, the 25cm estimate was made by Ven Thanissaro on the basis of the monks’ rules only (it’s been many years since I looked at this!) However in bhikkhuni pacittiya 22 an allowance is made for a bathing cloth. This is 2×4 sugatavidatthis, which on this estimate is 50cm × 100cm.
As it happens, I have a towel of exactly this size. It doesn’t even reach around my waist. It’d probably have to be double the size to function as a bathing cloth. Remember, such standard sizes, as is made clear in the Vinaya, are not meant to cater for an average sized person, but are an absolute maximum that must cater for even the largest and fattest monks and nuns.
It’s certainly likely that robe sizes were somewhat smaller than they are today, but we should beware of false precision.
One of my friends, Monk Jason, wears robes that are of “reformed” size, basically just as big as they need to be. He’s happy with that!