Just need to use your imagination; no hard and fast rules. It's ironic that I have met people in the past who couldn't understand how I and a few other people could recreate and inhabit a virtual fantasy world playing AD&D using little more than pieces of paper, pencils and dice. Now that the world is made for us, people complain that they are now restricted by this. Of course it is restrictive in some ways, but you just need to work within the confines of that. I'd say your only major barrier is other players randomly wandering in. You may need to make use of the instanced areas (once you've cleared them).
so many hate topics from people with 1 post recently.
What you describe reminds me of a webcomic I once read, Elf Only Inn (http://www.elfonlyinn.net/).
It dealt with a group of RPers on an IRC chatroom. The comic underwent a 2 year hiatus around the end of 2004, which was later discovered to have been largely influenced by the writer getting into WoW (amazing how that game svcks up your free time - my offline RP group went through a similar innactive phase because of WoW).
When the comic relaunched, the setting had changed to a generic fantasy MMORPG, though the previous cast and continuity remained the same... one of the ongoing themes was the adaptions made by players from a formerly free-form text-only setting to one with a restrictive game ruleset and lessened emphasis on 'roleplaying'.
Maybe you could read it and take some inspiration?
Other than that, generally I can say that RPing in a MMORPG is possible, but it helps if you are willing to move away from the traditional 'storyteller guides a group through an adventure' dynamic, and approach it from the perspective of a player; be your character, develop a backstory and a motivation that make sense within the context of the game, interact with other players exclusively in-character, hang around with players who do the same, and generally enjoy spontaneous free-form RP as you play the game, rather than relying on props and contrived stories to guide your roleplaying.
leaving items in the game world would be a horrible idea.
As over: why use ONLY immagination?
We MUST be restricted on an hi-graphic/low-freedom platform? It's the only right way to do?
Is not possible just try to think ways to harmonize the two aspects?
... I BELIEVE!