I agree with you the pillars are unfortunate. The replacement tiles will stand out no matter how close they come to matching so you're better off making sure they are clearly different so the gray one is better. Putting busy mosaic tiles could look nice but will interrupt the flow between rooms which I'm guessing is your problem with the columns in the first place. You will need to create a dextrous solution to tying into the 2x4 wall on the left side but I think it can be done tastefully- maybe beveling it back once you get past he end of that wall.

If you are looking to keep the "period" look, then I say no. My place is from 1916 & had a gross 1980's reno. I ripped out all the ugly vinyl floor & cheap Sears sink & went with a black hex floor, white subway, dark grey grout on both. Toilet & tub were original, but I got an old "Standard" wall mount sink with chrome legs & towel bars & an antique medicine chest, light fixtures & glass shelving & towel bar off Ebay. My total job...about $5k. Help my tile guy is my neighbor, but those 10, 15, 20k bathrooms were out of the question.

I think it is outdated too.. But some people love the strip. I just planned my showers and had no strips. Instead I did a tile change half up the wall (tile chair rail between) and in my master did this picture frame look (pic below)

I've always had a tile and glass shower and it's a bit frustrating to clean. However, like you, I love the look of tile and glass so I deal with it. What did you decide to do?