TwoSix
Everyone's literal second-favorite poster
Personally, I would do them as feat chains, or simply handle them diegetically. A possible, crunchier option would be to make "mini-classes".I like this. I don't know how archetypes will work with this system--but maybe we don't need archetypes, at least not in the way that they're currently done. I could see having "pseudo-archetypes." "if you want to play a swashbuckler, pick either Fighter or Rogue and then take these feats" or "if you want to play a brawler, pick monk, fighter, or barbarian and then take these feats."
Yes, this is absolutely meant for using XP as a spendable metacurrency.I'm not 100% sure I get what you mean that 1st level starts at 1k XP. Is this to allow for 0th-level characters? Or were you thinking about bringing back level drain and didn't want PCs dying because they were drained below 1st level?
Also, I know this isn't what you meant, but when you say "spend XP" it makes me wonder if XP could be spent as a meta-currency.
General idea is this. Starting characters will start at 1000 XP, enough to purchase 1 level in their first class. Buying the next level always costs 1000 XP times the level you're gaining. Buying level 2 costs 2000 XP, buying level 3 costs 3000 XP, etc.
If you want to take level 1 in another class, you just have to spend the 1000 XP and justify it in story, usually with some sort of downtime.
I keep track of total earned XP for a character behind the scenes, but I've found spending XP to be easier to track for players once they get used to it.
My OSE house rules for multiclassing are pretty similar, with taking level 1 in a class costing half the amount of XP it requires to get to level 2. (So getting a fighter 1 level costs 1000 XP, a cleric 1 level 750 XP, etc). The main limiters are no more than 3 classes, and demihumans must take their demihuman class as their first class.
I've used these same general hit point rules across multiple games of 5e and OSE, and they've been pretty popular.So, would this hypothetical fighter 5/rogue 4 have 9 Hit DIce (5d10 + 4d8, presumably), or simply 5 Hit Dice total? Because that's going to make multiclassing unpopular to the point that it shouldn't even be a thing.
1) When you level, roll all your hit die. Maximize the lowest roll. (If you roll a 1 on a 1d8, make it an 8.) The maximization mimics the 5e "max at 1st level" rule, although it's slightly stronger at higher levels. And it gets rid of the "2 HP fighters" of OSE, which I don't find fun.
2) For my OSE multiclass rule, roll all your hit die, maximize, and keep a number of dice equal to your highest level class. A 5th level magic-user/2nd level fighter would roll 5d4 and 2d8, keeping the highest 5 of that pool.
This is the house rules I use for OSE, where multiclassing is more similar to AD&D style in which a 5/5 multiclass would be about equivalent to a 6th or 7th level single class.
I've come to agree with @Lanefan that I feel that style of multiclassing is generally superior to the additive style of 3e/5e. But as a fan of diegetic progression, I don't like having characters be boxed into multiclassing right at character creation, so I made my own "hybrid rules" that are closer to AD&D dualclassing without the colossal amounts of suck.