Probably, the Warlord can use the Fighter base class as the chassis. It looks something like the following.
Note. The Advancement chassis alternates base class features by level − specialization then standard then specialization then standard capstone. The following table only lists the base class levels without the specialization levels. All of the specialization features of the archetype to distinguish one kind of Fighter from an other will be inserted in the levels between these base class levels.
A player always can play the archetype from level 1 up, even if only in a rudimentary way, such as picking a special atwill (maneuver, cantrip) with the appropriate flavor. 5e sometimes delays this decision to level 2 or 3, with awkward consequences. For the level 1 Fighter specialization level, more choices for the ‘Fighting Style’ can explicitly implement the ‘archetype’. So for example, the ‘Fighting Style’ of an Eldritch Knight at level 1 might be Mage Armor. The ‘Fighting Style’ of the Warlord at level 1 might be Commanders Strike or other appropriate 4e maneuver.
At the moment, level 3 squeezes in both Action Surge and Extra Attack. I dont want to move Extra Attack to level 7 because it is a quintessential Fighter feature. Meanwhile, Action Surge already delays from level 2. Either I will make the balance work, or I will juggle it around later. Heh, as it is now, it is quite a capstone for the novice tier!
Finally, I am only assessing the balance at the novice tier. Each class level will have features worth about a feat. The higher tiers correlate moreorless with the standard 5e Fighter. The Fighter really is powerful, including at high tiers. Probably, I want there to be more options here or there, to trade some of this damage-dealing for various utility effects.
If any Fighter fans or Warlord fans have any ‘Wizard envy’, let me know some of the stuff that a Fighter or Warlord should be able to do!
[TABLE="class: Table"]
[TR]
[TD]
TIER
[/TD]
[TD]
[/TD]
[TD]
FIGHTER
[/TD]
[/TR]
[TR]
[TD] NOVICE (class)[/TD]
[TD]
[/TD]
[TD] Hit Points 6 (d10)
Light Armor
All Simple Weapons
Grapple
Athletics[/TD]
[/TR]
[TR]
[TD] NOVICE (class capstone)[/TD]
[TD]
[/TD]
[TD] Extra Attack
Action Surge[/TD]
[/TR]
[TR]
[TD] HERO (class)[/TD]
[TD]
[/TD]
[TD] Indomitable[/TD]
[/TR]
[TR]
[TD] HERO (class capstone)[/TD]
[TD]
[/TD]
[TD] Extra Attack (2)[/TD]
[/TR]
[TR]
[TD] MASTER (class)[/TD]
[TD]
[/TD]
[TD] Action Surge (2)
Indomitable (2)[/TD]
[/TR]
[TR]
[TD] MASTER (class capstone)[/TD]
[TD]
[/TD]
[TD] Extra Attack (3)[/TD]
[/TR]
[TR]
[TD] IMMORTAL (class)[/TD]
[TD]
[/TD]
[TD][/TD]
[/TR]
[/TABLE]
In sum, EVERY Fighter will have the above features, regardless of archetype.
In this sense, the Warlord probably be a Fighter, but with the specialization ability to grant ones own Action Surge to an ally.