I will keep this simple and vanilla+TiCon.

Heart Canisters

Pretty much self explanatory. But unlike the previous versions of tinker, you just need one type of heart canisters.

It stacks up to 5 to add 5 hearts per modifier slot.

Reason I said 5 instead of 10 is for balance.

Crafting should be similar to what Heart canisters uses aluminum to craft canisters, apple, wither bone, and heart. Which the hearts can be food that heal health, but not hunger and saturation.

Heart Canisters can be added to all armor parts. If armor breaks, it will stop providing hearts, and can kill the user if they have low health. Ex: 6 hearts, the armor that gave hearts gaved 10 hearts, 6-10=instant death.

So this acts as a double edge sword figuratively. Keeping in mind maintenance of the armor as much as the player's health.

I don't know if it's possible, but this does make sence of what tinker used to have.

there's already an heart canister mod on 1.12.2 inspired from older Tinker's construct hearts feature.

Great would be the old inventory tabs too.

And @LemADEC whats the name from it ?

https://minecraft.curseforge.com/projects/baubley-heart-canisters

Good, though I do like the idea of a version of being integrated into armor. Mainly due that some armors from other mods are so powerful that health boost is basically useless.

So having a set of armor that gives that benefit can catch up to higher tiers.

@TheIllusiveC4
If for whatever reason tinker reinstate the heart canisters, I imagine you can adapt to it.

Either way I really felt that if heart canisters do return, your armor mod is perfect.

(Accidentally clicked the close button as I commented)