Indeed, any friendly Warrior can pick up the banner - which isn't too strange thematically, they are allies after all.
And otherwise, where would the distinction lie? Mordor Orcs can pick up banners of Morannon Orcs, but not Mordor Uruk-hai? Possible in the case of Mordor-Uruk-hai, but not Orcs that happen to be from the Isengard list? Nah, much easier to just follow the rules and have it so that the banner can be transferred to all allied Warriors. You could limit it to models of the same list, or same race, but the normal rules should work fine in the vast majority of the cases.
Lord of Winterfell wrote:
I don't think that named hero's or monsters (Trolls) etc should be allowed....
Heroes (named or otherwise) can't get the banners anyway. Non-hero monsters can in fact get the banner in theory, but would you want your Mordor Troll to have a -1 penalty on winning fights?