On the advantage thing......
THe system is and always was broken. But it was invented on a sole purpose..... to lessen the math that had to be done prior rolling the dice to speed up Combat in a pen and paper session.

Now in a video game the whole purpose of speeding things up is obsolete as all math is done instantly by the computer. Leaving us with a just broken system. So why it is broken?

Let me explain:

We all agree that having higher ground or attacking from the back should have some sort of advantage!
But lets dive into the Math of the Advantage system.

Lets make it simple to understand. Attacker has no bonuses at all but has the height advantage. Target is a guy in PLatemail Armorclass 17

So you need to rol a 17 or greater to hit wich is a base chance of 20 %. With advantage you get a second role wich means:

FIrst chance to Hit is 20% (roling a 17,18,19 or 20)
Basechance of 80% to not roll a 17 or higher on first roll and a chance of 20% to a 17-20 on the second roll. Wich translates into an additonal chance of 16% hitting if your first roll fails.

Now we attack someone with a chain shirt (AC13)

you have a base chance of 40% to hit AC13 (roling a 13,14,15,16,17,18,19 or 20) on your first roll.
Basechance of 60% to not roll a 13 or higher and a chance to of 40% to roll a 13 or higher on second roll. Wich translates into an additonal chance of 21% hitting your target if your first roll fails.

So that what does that mean in gameplay? Having a heigt advantage technically means that instead of having a bonus because you are standing higher than your enemy, the bonus magically grows if you target has lesser armor. Or in other words the your Armor gets magicaly and expontentionaly weaker if enemy is higher ground than you.

Its makes absolutly NO SENSE gameplay wise. And WotC know it. But it was a way to reduce calculations and speed things up at the cost of realism.

Now in a computer game where calculation speed is no issue.... the only thing thats left is pointless unrealism.