Oh, right, the Warden. I'd picked up on the similarity to the Avenger's raison d'être, but missed the other one's antecedent.

The only real commonality - and it's not what I'd deem central to the other two - is the whole oath business. And finally I've come up with a paladin concept I'm interested in, as I now intend to create a gold dragonborn paladin/sorcerer specializing in air magic, called "Oath Windenfyre".

::golf claps::

Alas, it will take more effort to convert to 5e my dual bastard sword-wielding wood elf, Julien Fryze.

Actually, the latter shouldn't be too tough other than having to wait until 4th level when you get your first feat (which is my one knock on the game. I like that all the feats are significant, but it's annoying that some concepts have to wait until 4th level, unless they're human.) and taking Dual Wielder. Longswords are bastard swords now (which is more historically accurate, as the terms were basically interchangeable). The weapon D&D previously called a longsword had a bunch of different names, but was commonly just referred to as a sword.

Actually, the latter shouldn't be too tough other than having to wait until 4th level when you get your first feat (which is my one knock on the game.

It's all quite doable, but the primary issues are:

1. Wood elves are no longer ridiculous cheese weasels. Have to choose a different race.

2. As you noted, no more bastard swords (he would have to stat them as longswords, of course). That is key to the character (he calls the right one "Magnificent" and the left one "Sexy").

I think of a bastard sword as being a longer sword than the longsword, one that you have to take a feat in order to wield one-handed.

I thought it was a sword whose steel composition was unknown.

t /snerk

BT- Well, he can still call them bastard swords. As I said, the names were basically interchangeable historically. What was so cheesy about wood elves before?

Laga- That's what the term meant in D&D (well, at least from 3rd Ed on. In 1st and 2nd, they didn't require any special training and did longsword damage (1d8/1d12 vs large creatures) in one hand and 2d4/2d8 vs large in two hands.) Historically both longsword and bastard sword were terms used in reference to swords that were around 3.5' to 4' long with hilts sized for two hands, but could be used with one when necessary. Modern parlance tends to use the latter term for the ones on the larger end of the spectrum, but they were considered to be the same weapon in regards to how they were fought with.

What was so cheesy about wood elves before?

The strength bonus, mostly. They were min-max favourites in 3.5. In their honour, I had another wood elf character in a different campaign, by the name of V.B Fiercecheese. (The V. B. stood for "Venezuelan Beaver")

The character I feel I can't update, interestingly, is my primary Living Greyhawk character, Kerrick of Nyrond. He was a human arcane trickster. Arcane trickster is one of the options given for rogues; but now, their spell progression has slowed dramatically. Kerrick was a typical rogue for his early levels, then somewhat underpowered for four levels as he did his multiclassing. Then he got third-level spells, including Fly, and it all came together. Once he reached 10th level, he became quite the monster, courtesy of the suite of Orb spells and Improved Invisibility.

I can make an arcane trickster, but I can't make that arcane trickster.

On the other side of the coin, I think ranged rogues are now much more viable. You no longer need to be flanking or invisible to sneak attack reliably.