This page is meant for notes on synergies with the base 5e features, especially Classes. As I research into specific subclasses I'll point out which ones seem really good, and which ones need work. (Also if any of them have specific rules that need to translate to this setting) If there's anything that's completely broken, I may have to introduce some special rules.

D&DESTINY

Having finally read the rules, it's very much compatible, with the only major hiccups being the following:

1- What Are Balance?

2- Stacking Shields with the various features that grant Temporary Hitpoints, which directly feeds into the first point.

3- Redundancy in Grenades, Charged Melee, and Class Ability. Actually, this is probably the biggest hiccup in terms of compatibility.

4- Aspects of Power could count as Feats if you convert them accordingly.

Well, a character is only as balanced as the opposing force.

5E VANILLA:

Fighter: With the greater emphasis on weapons and normal Attacks in this homebrew, Fighter's improved Extra Attack may be a very powerful option when it comes to shooting. They would burn through ammo in their weapons rather quickly, so instant reload options would likely be sought after. Warlock Fighter would be a solid option if they get their hands on (or in) Ophidian Aspect. Hunter Fighter would also be solid with their Dodge.

Barbarian: The obvious play here would be Titan Barbarian, but Guardian features don't count as Spells, so Warlock Barbarian and Hunter Barbarian would also be pretty viable, I think.

Paladin: This would be really strong for any Class, between Lay On Hands and Aura of Protection, I can't picture this being anything but amazing from a mechanics standpoint. The only issue is how Oaths would work in a setting like Destiny. Perhaps Oaths can be flavoured to be simply part of certain orders, like the Praxic Fire? Perhaps they be like Eris Morn with her own Oath of Vengeance. (aiat)

Artificer: Extra magic items to compound on the exotics that they already get, I see this one being very wacky. Even Alchemist would be pretty fun, I think.

Bard: I'm actually playing a Bard Hunter, and they've been the reason I made the Extra Attack feature on a Guardian. I didn't want to be a heavy spellcaster when the weapons and Guardian Abilities were already putting in the work. Utility casters in general are excellent in this setting.

Cleric: This class is already kinda cracked, so applying Guardian rules here would make them even more cracked.

Wizard: Much like Bard, utility caster builds would shine here. I can't stop Fireball, though.

Sorcerer: I can't stop Fireball. Can you? Quickened Spell would be really good to use since a lot of your actions are going to be taken up by weapon attacks.

(5e)Warlock: Considering a lot of these Guardian features are highly customizable much like Eldritch Invocations, the (5e)Warlock class seems like a cherry on top.

Druid: Wildshape doesn't strike me as having good synergy with these features. Circle of Stars has the Archer constellation that lets you shoot a Radiant bolt as a bonus action (meaning Light damage) Spores Druid would probably be really powerful against Thrall.

Monk: The improved movement options would be pretty killer, but I can't see Flurry of Blows being that useful in this kind of setting, unless you go all-in on Swords, Glaives, and Guardian Abilities. Also, Evasion. If the current OneD&D features make it through, Monk would be extremely good here.

Ranger: Non-Tasha features are extremely situational to begin with, though It would be really cool to allow the Favoured Enemy feature to include factions like Eliksni or Hive or Vex.

Rogue: Probably too powerful. Uncanny Dodge, Cunning Action, Evasion, and Reliable Talent would make a Guardian exceedingly difficult to pin down.

FEATS

If you pick Sharpshooter you hate me.

Nah I'm kidding. Knock yourself out! :D