Wow I too have the same glass above my doors. Mine are all internal swing doors therefore I don't have your delema. I'm in the middle of renovations and mine are staying. My walls will be dark and modern with all the trim white with the original character and it looks great. With your wall, it's a lot to deal with therefore would suggest replacing the slider with a glass door with timber trim, keep your walls light modern and bright and paint your trim dark (any colour you favour) here is my example to give you an idea of what I'm talking about hopefully you can see the value here is a snippet of my renovation good luck....hope my idea gives you plenty of ideas

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.

FormFunctionNT I love your lego door! So innovative. This idea may be a little busy for the other door, but just putting it out there... You fill it with squares of the 4 colours, but randomly leave 4 blank. Almost like 4 have left and moved 'next door' if you'll pardon the pun! Sorry, I couldn't help myself.