Mine is only 10" wide. This is a Rev-a-Shelf unit that my cabinet maker had to replace and make a custom unit instead. It only had a center track and it never closed properly, but it was a new design three years ago, and they may have worked out the kinks since then. These and the Hafele units come in several widths and heights. Notice that I have a deep cabinet over top. On my custom unit, the top and bottom shelves are 4" deep drawers. That would be better for the bath than metal bars so that smaller items don't slip through. But you could load that up with TP, cleaning and bathing supplies, hair dryers, etc., and have some flat shelves for towels. The shelves on my pantry have a small lip, unlike the metal bars shown here. The commercial pull-out pantries aren't cheap, but it looks like you've used nice finishes in the bathroom already. You might be able to have a door made to match your vanity. Barker Doors here in Oregon is one source.

I had the exact same problem. I picked out the vanity I wanted but did not think about the fact that it wasn't made to sit flush against the wall. I spent a month looking for something else, but in the end we decided to go with something shorter and have it not be against the wall. But we were going from 72" to 60" which is probably not workable in your mom's situation. I did find a lot of vanities that did have flat sides and could work in a corner, if you are willing to have the countertop fabricated. They just need to not have any trim detail on the top or bottom like the one you picked out does. I would just look at the ones without the pre-made tops. Because the pre-made top will still leave you with a slight gap because of the countertop overhang. This is an example: Avanity Modero which is sold everywhere, not just at Lowe's. The cabinet we ended up buying is an Avanity Madison which won't work for you, but I assume it is of similar quality. We are pretty happy with it. The drawers and doors have soft close but I do feel like the glides in my Ikea kitchen drawers are better quality. It is very pretty and I wanted a stained wood so I am really happy with our choice. If I had been willing to go with a painted finish, I think we might have stuck with the 72" Modero.

Most people prefer walk in showers. My vote is a walk in for ensuite over a tub. Whether or not it needs to be tiled sort of depends. I am a bit confused as you say what you want but then note this is a rental. That is planning for two things at once that may not necessarily coincide. A high end rental? Sure. Do the tile. Not so high end? Eh...I think the lower maintenance, the better. Tile and grout looks pretty as long as it is kept clean, but not every renter may be as motivated to keep things clean. If intended market is families, a tub or tub/shower unit somewhere in house is a good idea. Again, a tiled drop in depends on market. Also, you can do “tiling” as you said but please make sure you can also do “waterproofing” and proper tiling in a shower. A lot less room for error unless you want to be ripping it out when the wall rots in a year.

It looks like you have a lot of dead vertical space that can be captured. The clear drawers that bpath O Sophie suggests come in different sizes that can be stacked and labeling them is a game changer for finding things fast and staying organized. I find them more convenient than boxes that have to be unstacked, lids opened, etc. and since they're modular, you can swap out as your storage needs change. http://www.sterilite.com/ProductCategory.html?ProductCategory=19 is one brand. If you go that route, measure and take into account the door casing to make sure drawers can be opened all the way. and look at different configurations. The space left over on the right side can be used as a place to stack toilet paper, rolled towels, nesting the buckets, etc. Use the best location(s) for what you use the most. Place infrequently used items on the shelves hardest to reach. Of course, with little ones, the meds & cleaning products need to be stored out of reach. I also agree with suggestions for hanging a rack on the door, it's surprising how much can be stored there. The Container Store has great products and organization ideas for inspiration. Sometimes I splurge on them or look for similar products at discount stores, keeping in mind that square or rectangular maximize storage more than rounded containers. Post pics when you're finished - you may help us out with a thing or two!