What is the minimum recommended size for a walk in shower? I have a layout from my designer that, based on what I've read, might be too small.

The shower is 40" x 60" however, the entrances to the shower (there are two) make me nervous about overspray. If you look at the attachment, there is a door to the backyard against the south wall. And on the north side of the shower there is a partial wall serving as a barrier between the shower and the toilet. The opening adjacent to the partial wall is a doorless entrance to the shower.

My concerns are water splashing against the south door and maybe leaking out from under it. I assume this will have to be some kind of all-glass door since it's going to get quite wet. And it's an external door so it's probably going to have to be thick glass making it an expensive door? My other concern is water spraying out of the shower on the north side where the shower is open. Are these legitimate concerns?

Everything is so cramped because the bathroom is small and I want the designer to pack a lot into it. But I also don't want to cram so much in there if water is going to be spraying all over the place.

That being said, this is a bathroom that will get a lot of use but the shower will get minimal use so occasional overspray might not be intolerable. However, a future owner may plan to use the shower regularly so it needs to be practical for regular use too.

I have a request to anyone responding. I appreciate any advice specific to my shower. But in addition to telling me if it will/won't work in my situation, if there is such a thing, can you also say what the absolute minimum recommended size is for a walk-in/doorless shower? I searched like crazy and couldn't find a definitive answer. Every thread I found (not just on this site) started with "What is the minimum size?" but the question was never answered. The answers were always specific to the situation of the person asking. So maybe we can make this one case where the question is answered as definitively as possible -- what is the smallest recommended size for a walk-in shower? And is the answer different for a curbless shower?