That is a great idea, and if it's compelling people will flock to it, because a lot of people want a game that combines 5e's robust balance and solid design with heightened lethality and other old school elements.
That said, I don't think 5e is "easy mode" so much as it's built on a different framework of design. Old school dnd is built to kill the PCs, unless the DM runs the game otherwise. By kill I really mean challenge, but the game doesn't care if you are the right level to fight an owlbear, it just cares if there is an owlbear where you wound up, and if you managed to avoid fighting it somehow or not.
5e, on the other hand, puts much more of that transparently and straightforwardly in the hands of the DM. The DM decides how deadly every fight is, how terrifying powerful casters are, how crippling bad luck while journeying to the adventure site is, etc.
The point is, 5e is built to allow a group to choose it's difficulty, and trust me RAW 5e can absolutely be grueling and scary and lethal, rather than simply building the game to have a high difficulty out of the box.
I'm happy to share, and have quite a few times. PM me if you'd like.
The problem right now is that it's morphed into something a bit different. Especially magic/spellcasting since we were looking for something quite different. So I've really got to fork the design at an earlier point in the design. We also have a different class system too. Each has some defining features, and everything else is chosen by the player as you progress, with far fewer super-heroic options (although those would be easy to add). I'm not a fan of dozens of classes and archetypes, other than helpful pointers on how to mix things together to your liking. So we have three base classes, Expert, Spellcaster, and Warrior, which are based on their historical focus (although as I noted in the original post, in AD&D clerics were better at combat than rogues (theives). In our case, the idea is that it takes a lot more time to learn spellcasting, so they are the worst at combat, experts are better, but primarily have the most skills, and warriors are the best fighters (which was lost in 5e with the use of the proficiency bonus, since every class at a given level has the same chance to-hit provided equal ability scores).
Like AD&D, I'm not concerned with whether there are "trap" features or unbalanced things. If you have a group that doesn't like role-playing and character (as in personality) development, then you just don't use the skills/feats that speak to that.
The adventuring/combat/equipment/skills portions are the easiest to drop into an existing campaign right now.
The general feel that we're looking for is based around the classic definition of heroic - an ordinary person doing extraordinary things.
@Minigiant expressed that in a different way in
this post above.
I'm not sure I'd say Old School is built to kill PCs, rather than to encourage other solutions to problems than a straight frontal attack for every encounter. We tend to stay at 4th level (low level campaign) or 8th level (high level campaign) for years. We want the overall challenge (not necessarily every encounter) to be beyond the capability of the PCs. That is, they can't just fight, rest, fight, rest. They have to play, come up with creative solutions, look for ways to avoid the danger rather than taking it head on, enlist help, etc.
Death really has never been a common thing in our campaigns, in part because resurrection magic was always largely unavailable in our campaigns. So if you wanted to keep using a PC, you have to keep them from dying. Probably one of the main reasons we misread the DMG 0-hit point rule (although it seems to me that if the rule was written for exactly 0 hit points, it should have just said, "if a character is reduced to exactly 0 hit points...")
Regardless, I'm glad we interpreted it the way we did. Because it added a lot to our game. Trying to avoid being killed, combined with real, in-story consequences.
To us it still feels like D&D, or at least what we thing D&D should feel like. I've shared it with a number of people inside and outside of my groups. I either get feedback that says it's amazing and it's how they play now or no feedback at all.
