However, is there even one WEGO classic D&D style RPG with positioning and melee combat out there which works? Or at least a wargame but which is quite close to that, not any wargame?
As someone who really doesn't like WEGO for several reasons, I can point to the ancient naval wargame Mare Nostrum as an example of why it doesn't work.
Mare Nostrum is a wargame with ancient battlefleets, from Greek naval battles to Rome vs Carthage naval battles. It has a hex grid and you command ships in squads as well as individually. You can set their direction and speed, and the game tells you on which tile they will end up in the next turn.
So far so good.
The problem is that ancient naval tactics relied a lot on close touching maneuvers: ramming enemy ships or shearing off their oars with a close "drive-by".
But in the game's WEGO system, both you and the AI make their movement decisions simultaneously, and then watch them play out.
You don't set a target for your ships. You tell them which tile to move to. That means you have to guess which tile an enemy ship is going to be at during the next turn. Will the enemy stop his ship? Will he continue rowing it forward at constant speed? Will he turn away? Will he turn to face you? You don't know. So it becomes a guessing game, and in most cases both you and the enemy will just maneuver your ships past each other. Because WEGO just doesn't work in battles that rely on close combat and maneuvering.
It would work much better if you could tell your ships to target enemy ships and adjust their course dynamically based on enemy movements (like, you know, an IRL ship captain would do), instead of having them target a specific tile. But you can't do that, so it becomes a mess.
The only games I played where WEGO works are games with a focus on ranged combat. Modern squad tactics, or spaceship battles, where it's all about moving into advantageous firing positions, moving from cover to cover, or aligning a broadside with your railguns. Those work because you don't have to predict the exact position of your enemy, just their rough location within the map space: as long as your guns are aimed northwards, your units will be able to fire at any enemy crossing north of you.
But with melee combat, it just becomes a total mess of soldiers running in circles around each other.