I also like my Big 'Uns in Warhammer, but they'd probably be better represented with a magic item or banner. That way there's no question of how official they are, or anything like that, and it also stops Warmaster from suffering 'list-bloat', as you add Big 'Uns on foot, Big 'Uns on boars, Savage Orcs on foot, Savage Orcs on boars, Savage Orc Big 'Uns... etc.
If I really felt like mixing up my Orcs and Goblins to better represent their Fantasy counterparts I'd then discuss with my opponent beforehand whether I can take multiples of certain items (eg. These Savage Orc units are all regular Orc Warriors with the Battle Banner item), or even add 2 items to the one unit (eg. the Savage Orc Boar Boy Big 'Un unit has a Battle Banner and Sword that gives a re-roll to hit).
Further discussion on this probably doesn't fit this thread though.