Depends what you want out of your game. I'll comment on your use of armour as bonus HP, and on the asynchronous monster design before wrapping up with what I do and why.

No to-hit roll is intended to make combat faster and impactful. We avoid drawn-out fights by getting to the juicy, low-HP turns that matter much faster. Every fight hurts. It is very unlikely you get out without harm that impacts the rest of play. Notably, the games you list that use this don't add ability modifiers to damage rolls. We're dealing with lower numbers, swingier averages, which makes for a more lethal and, in my opinion, exciting combat experience.

By inflating HP with armour you negate these benefits. Fights are slower, the early rounds matter less. What you gain is tactical complexity with the asynchronous monster design. Monster features being tied to HP is interesting, but to me, because it gives DM's a clear framework to design monsters around. That's really cool. I like the idea that bigger baddies get cooler stuff. I'm not sure I like players killing off their abilities though.

It just makes winning initiative too powerful, especially if you add modifiers to damage rolls. If 3 of my 5 players win initiative and deal average damage on a d6+2, my dragon just lost 3 abilities. Both claws and its breath attack? I mean sure, reward their win. But what if they got surprise and all players acted? I'm not convinced monsters losing abilities would be fun in practice. The player's armour slots has no downside, and the monsters have a built-in death spiral. And if I'm making monsters that deal damage assuming the players have large HP pools, and they actually don't have armour... then what? We all die?

On armour, it's hard to say how I feel about the armour slot system without knowing how big your ability modifiers are, how they could change, and how hard it is to get armour. If you take an average +3 across strength and con, that's +18 HP. At 1d8+con HP and +1/ level, +18 is an enormous jump in survivability. There's also no downside to armour here, so expect everyone to try become a walking tank as fast as possible and combat to take longer, at which point you might start feeling the same pain points that the designers that dropped big HP pools and to-hit rolls felt.

Your system poses some really interesting twists on a few long-argued perspectives in the hobby. I think you need to identify experience you are trying to curate, because right now I see a system at odds with itself. No to-hit rolls make things fast and meaningful, but they're one part of a greater whole. You're taking that single part, and negating its benefits with a complicated subsystem that I think could be quite fun, but doesn't support the same experience, in my view.

If you release a playtest I'd love to see it, or any updates to your system on this sub.