both should just be warriors.
monk as a subclass or pack of feats on the warrior base.
This goes back to the old discussion: is this a variant on a particular archetype, or is it a full archetype with its own set of variants? If it's the former, a subclass can be sufficient, but if it's the latter you need a full class (this is basically the issue I have with 5e's psionic offerings so far).
What I mean is that yes, you can do "dude who fights unarmed" as a perfectly cromulent fighter subclass. But the fighter doesn't have room for all the various more-or-less supernaturally powered monk subclasses like the Way of Shadow ninja-style monk, the Way of the Elements bender-style monk, and stuff like that. If you want that kind of variety, you need a monk class for those to work off (though it might not be
named monk – I believe Level Up calls their an Adept).
At the point when classes stop being narrative elements, classes stop being useful. They become skeletons created in the hope to avoid creating a character that's good at everything, which can and has been done by budgeting and talent trees. No "class" is necessary.
WoW taught me a thing about talent trees: you need to put strong/iconic abilities deep into the trees, or they become poachable. This means that it can take a long time for them to "come online".
The classic WoW example are Enhancement shamans, who traditionally dual-wield using elementally empowered weapons mixed with direct elemental attacks. Their most iconic ability is Stormstrike, which lets them hit really hard with both weapons as well as (IIRC) give them an attack speed buff. In classic WoW, this ability was deep into the Enhancement talent tree, so you needed to be like level 40 (out of max 60) to take it. Before you had it, you were basically relegated to autoattacks with an occasional Earth Shock or Flame Shock, which was a pretty dull way of leveling up. However, this ability needed to be this deep into the tree in order to be an Enhancement shaman thing instead of being something any Shaman could get.
But in a later revamp, they changed things so instead of picking talents á la carte from a talent tree, you just chose a subclass and got all of its iconic abilities right away. Some may have been delayed to later levels, but you didn't need to pick and choose to get the iconic abilities. You wanna be an enhancement shaman? Here's Stormstrike, right at level 10 when you get the subclass.
So talent trees generally aren't a good way to provide characters with iconic abilities. They work best for fine-tuning things.