I was told that a new PC client is coming out in a relatively short period of time from now.
You could use the NumPad to move by default in the old one, expanding the message window was possible either by dragging its border or going into the client's setting, and it was possible to move while clicking but it wasn't super user friendly. Its main problem was that when you clicked offscreen it would display a message identifying the darkness/wall/whatever you clicked on, rather than moving you in the direction of your mouse until you couldn't move any longer. Some people managed to make it work, but I think most people relied on their keyboard.
Also, expanding the window was, of course, possible, but it wouldn't expand the game screen beyond 13x13 titles. That would stay the same and it would fill a lot of the extra space with gray nothingness (you would be able to get more chat space, though). The reason for this was one of economics. More tiles meant more bandwidth, which meant higher costs. I know nothing about what is going on now besides an ETA I was given on the PC client, but based on past experience I doubt that will be any different this time around unless people pay for that feature.