Many of a themes effects were just power swaps.... not power upgrades but they might be represented in 5e as a type of 5e feat.
I am a big fan of swaps. They are awesome for customization and balance.
If everything is formatted as powers, then it is so easy swap one power for an other.
Paragon paths might be a 5e feat as would Epic Destiny.
Not sure if the 5e feat will convey them well. But they might be built that way.
If you look at the ‘Advancement’ table. The way the leveling sequence works out has levels 20 to 24 for Epic tier. This includes two ‘Epic’ feats at levels 20 and 24. It also includes an Epic race feature − great for concepts like Archfey. Levels 21 and 23 are for the Epic ‘destiny’ − here renamed ‘immortality’. These immortality features focus on a method of gaining immortality, and an epic legacy or portfolio relating to this concept.
I assume it will be 4E or Pathfinder levels of feats so a human would get a bonus feat.
This Advancement table allocates class features (including archetype and path) at each odd level, because that is when the spellcasters get their class spells. This table intentionally, allocates spells according to the 3e and 5e method, because it allows for players to pick and choose various kinds of spells. 4e itself was hyper rigid − assigning dailies, encounters, and at-wills at specific levels − thus made spells wonky and difficult to balance.
I feel all feats should use the same format as spells. Then it is easy to compare them to spells, and rank them according to their levels. Then allow players to pick any feat of the same level or lower.
A cool thing about 4e is, there are no ‘spell levels’. All levels refer to the same level in the Advancement table. So it is possible to rank all spells and feats from level 1 to level 20 and higher.
In 5e, the class determines whether a spell is cast per long rest or per short rest. For example, Wizard and Sorcerer can cast certain same spells differently. But for 4e, the spell itself is short or long. So, I think it is ok for a Wizard to pick a short-rest spell and for a Warlock to pick a long-rest spell, if they want it for their known spells.