One shade for each window, that is if you have enough space for inside mounts, from your photo it looks like you don't. If that is the case you would have to go outside bracket, and then you would cover two windows with one shade

The windows don't look like they open it this area, so you don't need to consider that.

Here are some things you should consider:

1. Type of lift system you using. If it is a continuous cord lift system, you are suppose to anchor the cord down. This would mean if you did 4 blinds, you would have to anchor down the cord on the 2 center windows on the metal frame. This might not be a look you want.

2. Roller shades typically have a bigger gap on the sides, due to the lift system mechanism. This would mean a bigger gap between each window.

3. Depending on the size of your window you could possibly do 1 shade too. Roller shade fabric comes in some fabrics up to 120" wide.

For large windows like this, it can be difficult to figure out the right window treatments. You could go with a larger size that would cover all the columns, or one per two columns, as you said. Get some ideas here: http://www.halcyonshades.com/st-louis/our-portfolio/gallery/

yes, the shades work in both ways. added function, nothing lost. :)