In any case, yeah, Psion has the more pressing case, in terms of history, settings and world building, and in terms of gameplay/character-archetype niche.
The trick with Warlord is that it was designed specifically with its own edition's combat system in mind. It's probably the only core class that isn't an adaptation. That is why it is, understandably, THE class of 4e. It was perfect because it was the exemplar of what the designers were attempting to (and, imo, succeeding to) develop.
The Warlord would be a disappointment in 5e for exactly the same reason it was incredible in 4e; it would be a pale adaptation in a system that no longer catered directly to their specific gameplay niche. I would argue that this has, in fact, already happened; twice, in fact, with the Battlemaster and the Purple Dragon Knight. These were 5e adaptations of the Warlord. The designers wisely renamed them because:
a) honestly Warlord was a pretty bad name, but more importantly,
b) they knew it would be disappointing to the most hardcore of fans of THAT was the Warlord they got, so left the door open for themselves to try again (and again...)
In my opinion, the PDK is the 5e Warlord. I feel like anything more than that would either fail miserably in capturing the spirit of the original or have little to nothing to offer to the non-combat tiers.
What bothers me even more is that would reinforce the worst thing 4e brought to the game: the slavish devotion to "power sources" to the extent that a significant portion of the fanbase refuse to re-flavor classes/abilities or insist that anything be "canonically" nonmagical.