Why would you remove highground ? What would be the point of taking a good position in your system ?

I actually don't have an issue with high ground. It is not, however, a 5e rule to get advantage for high ground. To me, ut makes sense, but for full blown 5e rules for strict followers, that was why I mentioned it.

I'm all for a better balance and various difficulty level but what you ask is a complete other system with bonus actions that becomes actions depending your choice (UI ?), a useless verticality except to shove, specific creatures for every mode, an action to heal (maybe) 1HP,...
Being 100% faithfull to the rules is not necessary and as you described it, it looks boring to me.

I'm really just wanting things that make more sense. Eating food while in combat doesn't. Even drinking a potion as a Bonus is a bit hard to believe. You try chugging a bottle in 3 seconds. A potion should be an Action, almost 6 full seconds.

Its not a completely new system. Its a tweak of current. Instead of Shove being a Bonus, its an Action. Disengage is separate from Jump so characters aren't jumping 30 feet across the room.

The game has to be balanced first and it has to have strong foundations.

Absolutely, but many are already complaining about 5e is too hard even with cheesed homebrew rules to make it easier. So, how you gonna get good foundations without a solid base ruleset? Give us a 5e ruleset as the base and then cheese it for Easy Mode or whatever you want to call it.

Tweaks could then increase/decrease the difficulty (i.e +1/+2/+3 for highground, +0/+1/+2 ennemie's AC, +0/+1/+2 to allied ST or such things, barrel weight 100%,70%,20%,...).

Yes, except 5e should be the starting point. Easy would be offering advantage instead of bonuses. Hard would be increasing AC by 2 or whatever.

Even Pathfinder that has A LOT of options to customize your experience don't allow players to custom what is action and what is a bonus action (Don't know the EN words for Pathfinder but you get the idea).
What you ask looks completely unreasonnable and would require to balance the game differently for all difficulty.[/quote]

The point is that 5e is a solid, tested set of rules already established. So it should be the starting point. Then tweak it for other difficulties. The 5e system balanced things well. Its because they made things Bonuses when they should be Actions that everything is jacked up now. Shove is an attack. Therefore, it should be an Action like Melee Attack. Disengage is an Action because you have to work hard to avoid getting hit while moving away from am enemy. Making these bonuses throws off the whole combat system, making it easier. Thus, the game as is seems set on Easy. A 5e authentic ruleset would be more like normal.