Interactive 'skilled' combat system: real time combat system about same complexity as rts

No GUI: inventory? open bagpack, others can also watch and take. (ex: Spell building? building composing =⇒ virtual environment , …)

Independent world (no player disconnect, creatures, vegetation, economy)

Central cities, outposts, guards, resources

RTS elements

Grinding == combat training == in-game character combat intuition generation

Outpost + City battles

Minions through spawn crystal, use for defending outposts.

The world consists of some major cities (currently 2: the good main story city, and the Eeeevil city of the black monsters). Scattered across the world are outpost, which provide resources amongst other things.

You are in an interactive movie. You are NOT playing a computer game.

The game should do everything to not break the virtual world it creates. All pc specific things should be minimized. 
You are moving around in a real world, and you do everything as if it would be a real world.
Example: there is no inventory screen, you only have a backpak where you have to take things out of.
Note that the game is still allowed to 'hint' actions. This is what are in real-life automated actions, or intuition.
Example: auto-aiming of spellcasting, autotargeting for item pickup, or even for laying it out in shops, opening doors,...

Always Allow Multiplayer, everything can be done in team

This is also true for even GUI should be mp, preferably do this by making all gui ingame.
Example: Spell training happens in a magic created environment, telepathy,...
Trading is laying out items on the ground and picking them up.

Jump into game, play immediately, jump out (about 20 mins?)

Can do everything!! (can be guard, shopkeeper,… can be useless and boring, but its possible)