I have little desire to take the BM Fighter's 'superiority dice' mechanic, as it seems oriented primarily towards DPR. In many ways, 'superiority dice' are akin to the Warlock's pact casting: it effectively casts their limited 'casting mechanic' at its highest level. (And then recharges their 'spells' on a short or long rest.) I do see the BM Fighter's combat maneuvers, or at least a small subset thereof, as a meaningful starting point for the Warlord. '
Existing 5e maneuvers are essentially 'low level' (the Battlemaster can choose any of them at 3rd level), gaining 'scaling' mainly from Extra Attack, proficiency, increasing attack stat and any magic weapon or buff the Battlemaster might get, and are structured to synergize with the fighter's DPR focus, styles, Extra Attack & Action surge. They could be a starting point for Warlord maneuvers, but they'd have to be adapted to the needs of that concept - greater flexibility and primarily contributing support situationally rather than dedicated at-will DPR and the odd rest-recharge DPR boost bundled with a minor rider of some sort.
The challenge, however, will be in determining what that mechanic for triggering/limiting Warlord maneuvers would be, since the BM Fighter's maneuvers are triggered, limited, and powered by 'superiority dice.
When you put it that way, CS dice do sound like a fairly neat little mechanic. While the Battlemaster was presented as a 'more complex' fighter in response to the calls for a more flexible/interesting/balanced fighter that somehow always got cast as a desire for complexity-for-its-own-sake, it's still doesn't hold a candle to casters in terms of versatility, flexibility, agency, or resource management. The Warlord would need to at least have a candle, if not a torch, to hold up to casters in that sense, in order to be viable while primarily contributing support, especially to be able to be a party's sole support class.
That means the mechanics limiting and defining maneuvers need to have a bit more to them.
IMHO, one of the most important aspects of the Warlord concept is that it's primarily focused on allies in a way even other support classes aren't. A caster contributes support by expending a spell slot that adds directly to an ally's power in some way, sometimes even just uses the ally as a platform. The Warlord exhorts or coordinates his allies, but anything extra they accomplish because of that is still coming from them. Inspiring Word, for the clearest example, doesn't juice up your life-force or magically knit wounds, it gets an ally to 'dig deep' and fight on in spite of those wounds. In 4e, triggering an ally's surge modeled that, in 5e triggering HDs could - but HD are a /very/ limited resource compared to surges (or anything else, they are the slowest-to-recover PC resource in the game). Still, I suppose you could slip in the ally's HD instead of a CS die for Inspiration-related maneuvers that gave allies a bonus, they could give whatever bonus /in addition/ to restoring hps (or granting temps, if the ally was at full already), just as CS dice do extra damage in addition to whatever other aspect of a maneuver they determine. As a sole mechanic that would have at least two drawbacks: 1) if a module further reducing the recharge of HD were in play, the Warlord would be unduly impacted and 2) it only works for Inspiration-based, maneuvers.
Another thing I've considered is limiting tactical maneuvers not with a recharge based on PC resources, but with more of a 'burnout' (that's a Hero thing, you roll after you use something to see if it's still working, once you fail, it's done for the day) based on enemies seeing through the tactic (INT save strikes me as the best way to determine that).
This also makes me wonder whether 'stances' could effectively be the 'cantrips' used by Warlords. I.e., a Warlord adopts a 'stance' that provides small combat bonuses/buffs that could be changed mid-combat and that also supplement their maneuvers. Unlike maneuvers, the Warlord may be limited by their list of known stances. Stances may even require 'concentration' to maintain. Or there could be a small list of 'known' cantrip-like maneuvers that the Warlord could use without expending whatever their maneuvers per short/long rest mechanic may be.
Those both sound good. A 'stance' could have some ongoing, passive benefit - it could be a way of working in a Commanding Presence or an 'aura' type of ability - while a maneuver could be immediate and active.
If you were to go the 'known' or 'prepared' route with maneuvers, it could also be a way to make the class more customizeable. If, for instance, you didn't like the idea of rest-recharge or other limited-resource maneuvers, you could choose all 'stances' and at-will maneuvers. The Warlord could learn new maneuvers by researching histories or by inventing new ones (audacious ploys and brilliant, novel, tactical tricks are commonplace themes in genre - that typically only work once) or by observing (and making his INT save against) another Warlord using one, so the full list would still theoretically be open, much as it is with wizards, but the more maneuvers there are in the campaign, the less likely one Warlord is to know all of them.
At-will maneuvers would obviously be less dramatic in their affects than those that consumed HD or had a rest-recharge, or that enemies could foil with an INT save or whatever.
'Preparing,' as I suggested above, should be more a matter of training, of working with allies so that they can benefit from the maneuver. That could happen at a long rest or, with more bookkeeping, during downtime days. It could be with allies as a group, or you could have some allies participating in certain maneuvers and others in different ones.
