I think scouts should be kept separate--plenty of people like to carry them, even if they don't have a unit. And it sucks to not have enough scouts. And, some armies may deploy dedicated scout/skirmish units, where one or two nobles has only a 15-man unit, but 5 scouts, while the bigger 50-man units may only have 1 scout.
I'm also concerned about the cost of building multiple banner manufacturers/siege workshops/etc. If your entire army goes to one city to resupply, that city will be stripped bare, yes?