This sounds like a personal hell to me.
I mean, it might work if your group is all kind of on the same wavelength to begin with. But if that’s the case, you could also easily start with a system you like and go from there instead of reinventing all the wheels.
A lot of people have only really played D&D and its close relatives. I like to describe that in this metaphor: Imagine someone who has only every seen the lord of the rings movies. They’ve watched them over and over, both cinematic and directors cuts. They know all the lore and all the minutia. And then they sit down to write their own movie. Maybe a sci-fi space mystery to change things up. And this movie? it has horses. Because movies always have horses, don’t they? They’re in like every movie. So when the detective is stuck in the burning theater, his buddy should ride in on a horse and save him.
So I 0%, maybe even some negative percent, want to have to sell a group on “RPGs don’t actually need six attributes” or “you don’t need to have separate rolls for to-hit and damage” for the first time in their lives.
Secondly, most people are bad at design. Sorry. It kind of follows from sturgeon’s law (“90% of everything is crap”). Most people don’t set out to make crap, but it happens anyway. Most people firing from the hip are just not going to make good systems. Especially if, as above, they’ve only ever really played one kind of game. So, no, I don’t want to deal with the guy who’s like “On a natural 1 you should drop your sword” who doesn’t realize that, because fighter types make a lot more attack rolls, they’re going to drop their swords way more often than you’d expect of the archetype. I am reminded of an unhappy time in an old, bad, D&D game where I fruitlessly tried to explain effective HP to the wizard. (Since D&D 5e stops counting damage at 0, there are some weird interactions between initiative, healing, and damage.)
Third, even if you avoid all of that, even if you have a group with a deep and wide knowledge of game design, you’re going to end up with an inelegant mess. Why does intimidating someone mean a simultaneous roll-off of increasingly large dice, but bluffing someone means drawing poker hands? Because those rules were added on different sessions, and Mike was really into poker and convinced people it would be cool. Wrestling someone you flip coins, but knife fighting you roll d4s. Sword fights use this complicated table Joe insisted would be fun, but magic is just a roll off. No thank you.
I’d rather just play Fate, which is already pretty loose about how to interpret conflict and consequences.
Ah yes. I believe the term for that is “fantasy heartbreaker”. Fascinating history, really.
http://www.indie-rpgs.com/articles/9/
https://rpgmuseum.fandom.com/wiki/Fantasy_heartbreaker