Blizzard here in Maryland. Got time to post now, not trying to top-post I swear.
Those (existing mundane) sub-classes are too locked into DPR as their primary in-combat contribution.
All classes should contribute damage in the combat pillar. Your wording "locked-in" seems to acknowledge the existing 5e framework. They may be focused on damage (I disagree), but those classes are the only acceptable tool we have. Well, besides the eternally vague DMGuide guidelines.
The Warlord already bucks trend in a million ways. He gets pitchfork'd when we try to add more "special treatment" to him. I'll concede that tactical things can be implemented. As you said, all classes do their own fiddly bits anyway. But I'm not crossing my side of the fence in this "Vanilla Warlord vs Novel Approach" debate.
There is a niche for someone that can support others in a low magic campaign. Why does this have to be a class called Warlord?
Base Class: Strategist, Field Expert, Expert (3.5), Supporter, or Buffer (Like Fighter and Commoner)
Subclasses: Warlord, Intellect, Technician, Survivor, Ranger!
you 'want' a warlord, but I would prefer to buy into a support class that was not so limited.
Good point. Global Support vs. Combat-Pillar-Only support. That's tough.
Re: It steals the bard's sctick
Not really. Bards get more ShortRest options, more spells, music, more charisma options, more Exploration, can be chaotic, can't wear heavy armor. They are too Rogue-like. The warlord would be lawful, heavy armor, Intelligence based, no music, only 1 or 2 shortrest buffs / auras, and Exploration pillar will be limited to only "can Identify leaders in a group of people".
Besides, 90% of class fluff is the artwork on the first page. We all know the 4e Barbarians were notorious for their broken-jaw class feature. Just draw a warhammer in the artwork instead of a banjo, and viola.