I have a whole wall that I need to block off with some sort of door. I'm thinking that a bi-fold door would be awesome. However, my husband kind of wants a sliding door. I just think how cool it'd be to have a whole wall made up of a door that could easily be tucked away when needed. This would make outdoor barbecues a lot easier. It would sure save me from having to open the door every time. http://www.superiorwindows.com.au/content/Products/BifoldDoors.aspx 

A cavity sliding door will be the solution to the shelf problems. But in any situation it requires to be built into the wall. Brick wall is I presume a bit more work. A wall mounted sliding door will take up space on the wall. It's just about working out where is best. Need the wall shelves in the ensuite? Then it's outside, and pull the furniture out from the wall a little so it can run along the wall. Really need a bookcase or other wall unit right on that wall? Consider if you can move the bathroom shelves. :)

A sliding door is just a big window, and if correctly built in (check if the glass is the correct sized for the door if a bit old) with the correct sized lintels this should not be a big problem as the loads would be transferred to the sides, allowing the door to slide easily. Silicon spray (being a Yachtie were we use this stuff everywhere), we now use silicone spray on all our windows in our 1930 home and the windows glide across with one finger before they used to tilt when trying to open them. I would place the door head up to line up with the others and one thing you might consider is placing a window seat, (rebate the bottom channels into the window seat) and have the window seat in and out, place a cushion over the entire seat, should be fantastic and if the deck is built, than no balustrade is required. If it is a stacker slider, i would do the seat for the entire length. So instead of looking a bit funny they will think it was supposed to be like that. We should all think outside the square more often. RAM

If your block is facing North or West (within Australia) maintenance will be required to ensure movement is minimized. Timber doors are beautiful they just tend to be susceptible to sun damage. FYI Cutek is a great timber protector if you want to keep the natural look however you will need to keep applying year after year.