Oh, I could see it, theoretically. For instance, a faux-Warlord fighter sub-class that could sacrifice it's Extra Attacks to do all sorts of maneuvers, dynamically. Extra Attack represents a pretty big chunk of power. It's just unprecedented, ATM, and it's not like Mearls is suggesting anything of the kind in his podcast.
And, yeah, it'd be tantamount to creating a new class. Heck, the BM's maneuvers are barely contained in the existing fighter, in either sense. They're both a bit much in terms of column-inches & complexity for 'just a sub-class' and constitue an entire, unique sub-system. The mechanical distinction between a Wizard and Sorcerer (ie, the metamagic sub-system) is arguably less profound than between a Champion and a Battlemaster (maneuver sub-system). That maneuver sub-system is then left with no room to grow or be adapted to other things.
A whole class that got most of it's capability from a larger list of level-gated BM-style maneuvers, for instance, could have sub-classes that cover a variety of Warlords, and other martial archetypes like the Bo9S Warblade and the Weaponmaster and 3.x fighter-based builds you just can't do yet, even with feats - heck, even the mythical 'martial controller.'
And, frankly, as neat as that may sound, I think they could do better.