I think it's not often done because it sounds like downsizing(needing less tiles/graphics/range-calculations)
that said, if well implemented(like the ideas mentioned) it can be a real addition to a game

Yes. The main reason why I am doing this is because I started with traditional RPG systems and ended up abandoning the project twice because I realize they require too much art assets (and to a lesser extend, bandwidth).

Hopefully, the third time's a charm. :D

you fix bandwith by having players first download a complete client containing all the art(downloading that all once)

making a good system(as ideas mentioned) will actually be more work i expect, just "skipping corners" with this system will only make the player feel cheated(as he should feel)

you fix bandwith by having players first download a complete client containing all the art(downloading that all once)

The bandwidth issue comes from keeping track of players moving through all those tiles.

If the room is made of 5x5 tiles, it takes 7 moves (keypresses or clicks) to enter, cross and exit the room. If the room is just 1 big tile, it just takes 2 moves (keypresses or clicks) to enter and exit. Every time a player moves his keypress/click is sent to the authoritative server for processing. With 20-30 players on a traditional tile based map with hundreds of tiles, the server hits could add up.

Also, if the room is just 1 big tile, I can afford some latency. Even 500 ms latency could work. But players constantly moving around a room of 25-36 tiles would need pretty good latency. If there are 5 players in the room with you, the server needs to push data to your client every time one of them move a tile.

The biggest problem is still the large amount of art assets required to build a fully traditional tile based world...its too much for 1 hobbyist dev to pull off.