I guess it all depends on how 'historical' you want to get with the mod. The ashigaru definitely wore the same sashimono, and like you said samurai had their family sashimono. And of course I agree that it will be easier for the player to quickly recognize his units, but then again look at Rome 2. There is such huge variety in armours of factions, and many faction types (e.g. hellenistic factions) have the same armour type. When you see battles in R2 it's a total cluster
where you can hardly recognize who is who unless you look hard (at least among the factions with similar armour). The big unit flags are therefore there to easily recognize friend from foe, but if you want to go to cinematic view and enjoy the battle, you will have a harder time
Also look at the medieval 1212 mod for attila. It looks beautiful with such a huge amount of variety. People love it exactly for that reason of accuracy and detail.
When I say different sashimono in units, I don't mean a ton of variety, but maybe 2-3 different types (or colors if you will, cuz like you said the mons were usually the same within a family) just to demonstrate the branches. Maybe you can do something like this: The major clans like takeda, oda and shimazu can have 1-2 sashimono, as their armies were bigger and they were more united (in case of takeda for example you can add a sanada sashimono as they were retainers); and the smaller clans like kono, yamana or ito can have a bit more variety, displaying sashimono from the minor clans from their starting regions (kind of displaying a union of more smaller clans under one banner), if you get what I mean. I know you can't make like 100 factions (and that would be kinda pointless), so my idea is to display the historical colorfulness of japan with the different sashimono in units (the experience flags are already a great addition).
As for the clan colors. Well, I would say screw shogun 2 and go historical
Why make flags that are exactly the same as S2? I would play S2 if I want such colors. People like new things and more variety, believe me
Of course, this all depends on you as it's your work.
I'll take a look at the clans you plan to make (unless you changed something) and see how I would 'paint' them. But shimazu for instance I would make white/black, like you already did on the small flags. Uesugi and date are a bit problematic indeed. For what it's worth, Kagetoras hata jirushi was white with black mon. So maybe strat flag can be that, and the experience flags and sashimono can be blue/red and white/black. Date can be blue/gold (pretty much like in S2), with blue or black, and white sashimono.
Here's a thread of E. Valerio on samurai archives with a ton of pics
http://forumarchive.samurai-archives...er=asc&start=0. Sadly the pics are blurred for some reason, but when I go on my phone they are visible (?). But I guess you already saw plently of those.