Do you think anyone will suggest flavourful builds using the Emerald Enclave feats? No, because they're garbage. Or the Harper feats, without relying on hobgoblin? No, because they're garbage for any other character.
Yes. I think the Emerald Enclave feats will have flavorful suggestions related to druid familiars and ranger companions. Scouting pets is still considered good, yeah? The origin feat is bad, but I don't really consider them to be huge game defining abilities in the first place.
Harper feats are only bad because Help is bad - it needs to be a Bonus Action instead of Action. There's a
reason why D&D developed Healing Word and turned potion use as bonus actions. In that case, though, they're actually rather good feats. Arguably too good, if you consider the at-will granting of Disadvantage on spell saves OP.
In fact, you could almost see them as part of some kind of ... commander class. Something about being a lord of war or something...
Okay, joking aside, if I was going to make a good banneret / warlord option, bonus-action Help is going on the menu, and absolutely using these feats. Remaking the Mastermind Rogue is on the menu. I've seen homebrew bards with Help as a BI. There's more potential to mix and match. Maybe we'll see new Weapon Masteries at some point that work like the Help action.
Cold Caster on Elements Monks isn't going to be the "diverse" build, it will be the default, in the same way every Elements Monk is expected to abuse Grappler. 2024 5e actively discourages diverse builds, because not taking the Right Options means your character is simply going to be much worse than other players' characters.
Okay, so the Elemental Monk is expected to abuse Cold Caster AND Grappler now? Man, that's going to be super feat heavy on a class that's already stat hungry.
It seems to me that you have meaningful and diverse choices right here, choosing between some very good options.
(Also, advantage while bloodied is actually mediocre because almost every martial will be using a weapon mastery that provides advantage on most of their attacks—and almost every other weapon mastery isn't worth using in most circumstances even if you have auto-advantage.)
Unless the Martial in question is Push Mastery for other kinds of shinanigans; I know some people that are using Pike with Polearm Mastery for consistent Reaction attacks.
Advantage is easy to get, but its not something we should assume is coming from Mastery specifically. If you have a second source of Advantage generation, that leaves you open to use something other than Topple or Vex for more shinanigans.