I'd like to see how it'd play without it before condemning not having invisible walls and having a slightly wider (compared to the almost 16:10 aspect it had before) as being show stoppingly game changing in a negative way. I think it's only people's fears that it may not work gameplay-wise that are the biggest deal when it comes to widescreen. Besides even with invisible walls the character would still have to traverse the extra space when for example Scorpion does his teleport which is the one thing that would mostly be affected. About that I was thinking the same way as Interloko that if nessasary one could tweak the velocity to compensate for the extra width although again it's not that much more than the OPR so it may not be necessary to do it or perhaps only a little bit.
I think this lacks texture and dimensionality to it. I think it'd be better made as a 3D model with textures and matching the look and feel of the rest of the stages. The trelace should I think look like it's made of iron and painted... the small ones in the palace gate sort of look this way in your remake and have a nice three dimensional look to them. Also this is for the courtyard, no? Shouldn't it be red? The middle barry part is supposed to match the other piece that's also reused in the palace gates looking at the original sprites. I mean look at this page where it shows them next to each other:
http://mkw.mortalkombatonline.com/mk1/arenas/thecourtyard/
BTW, I didn't like having too much push back in the corner as it prevented me from going crazy with juggles especially in MK2 although I understand that it's probably part of the feel of the game.