Survivable 1st level characters.
Or, damn it, useless 1st level but everyone starts at 2nd
This is one of the hardest/easiest. Almost any TSR or OSR game has fragile 1st level characters, but simple house rules to mitigate death are common and easy to add in. Death Saves, Only Bleeding and Unconscious Until At -10, Starting HP = Con score,
various Wound/Injury charts to roll on at 0HP instead of simple death, etc.
Newer games like
Worlds Without Number or
The Nightmares Underneath or
Knave normally make characters a bit tougher to start out with.
Epic10 ish - ie a low powered , low/mid magic world
This is pretty common.
Shadowdark,
Five Torches Deep,
Dungeon Crawl Classics,
Shadow of the Demon Lord, and a lot of other games do this. Although DCC has a higher power scaling within that range, as I recall. A 5th level DCC character is usually substantially stronger than a 5th level D&D character, to my understanding.
Unified xp table
Milestone levelling (because i think that xp-as -reward doesnt actually work)
Unified XP tables are common in the newer OSR games which aren't actually just clones of TSR editions.
Milestone leveling would just be you telling the PCs when they level up, right? So it works with any game that's got levels. You just throw out whatever XP system the game comes with.
This is rare, IME. The
Goblin Laws of Gaming allow you to mix and match class levels, though by the book you only get up to four class levels/templates.
Shadow of the Demon Lord or the less-dark updated variant
Shadow of the Weird Wizard apparently use a similar concept, though, where you choose a Novice Path to start out with, an Expert path at level 3, and a Master path at level 7, and are allowed and expected to mix & match.
A verisimmilitudonish approach to encumbrance and stuff
Does this mean you'd like a slot system, say, so encumbrance isn't just handwaved or a weight counter without consideration of where stuff is carried?
The slot system in the GLOG is pretty good.
Knave 2E has a slot system, and injuries or fatigue take up item slots! Which I think is pretty elegant- as you get more tired or injured you can carry less stuff.
Here's a neat location-based one from an OSR blog I found a while ago.
Quite fond of AD&D magic user spell hassle
How do you mean? Like having to memorize and being vulnerable to attack and losing your spells while you're casting?
That's pretty easy. Most OSR type games are designed to support Theater of the Mind rather than battlemat combat.
Setting: vanilla , bit could be sold on weirder if the rules support the setting
Sounds like you'd like
Shadow of the Weird Wizard better than
Shadow of the Demon Lord, say.
I might suggest having a look at
Shadow of the Weird Wizard,
Worlds Without Number, and
Knave 2E.
Knave is actually classless, but that means you can also mix and match capabilities.