Well, if you want to add a Warlord you have two initial problems. One, it needs to be mechanically different enough from the fighter to not just seem like a tacked on bit of fluff. Two, the current class and subclass system doesn't actually leave a lot of design room for what a Warlord should be good at without stepping on some siloed class toes. Personally, I'd want to unbuckle subclasses into a list of abilities and let people take them that way, which would actually leave a ton of design space to realize a Warlord just by adding abilities. I'd probably go with a list of general abilities and then bespoke lists of class specific abilities (replacing subclasses). The abilities themselves would probably need pre-req's to make things work.what kind of adjustments to the class system are we talking about?
A step farther is to unbuckle classes themselves into a master ability list, but I can't see WotC going that far.