Hi, if you did a pony wall on the side next to the toilet you would take out some of the 42" width which I think will be ok. A Kohler cast iron sized shower pan is 36x48. The pan can give you a good idea that your space should be big enough to shower in. I have seen references that the smallest shower should be able to contain a 30" circle with in the showering area. I like the idea of a pony wall instead of a glass wall next to your toilet. I have no thoughts on the location of the shower head. The toilet should have 18" centerline to the wall. Here is a link that I found very helpful for my layout. Here is a link that might be useful: illustrated Rules of Good Bathroom Design

I understand why some folks say wait a year for a major remodel. I moved into my house in May. There were some things about the house I really thought I couldn't live with but after some time they don't bother me. However, I only have one full bath and I knew from the start I wanted to install a master bathroom. But the process of designing, getting bids, getting permits, ordering materials, and then scheduling the work doesn't happen overnight. I have a contractor and he had the designer he works with come over to discuss the bath back in June. She came up with some options and that took a few weeks to decide on the plan. Then my contractor was on vacation so took a couple of weeks to come up with the bid. I said was ready to begin. The contractor and designer just came back last week to finalize the plans. The building permit takes 6-8 weeks in my city and we have to decide on and order materials so the work probably won't start until January so that they won't be destroying my house over the holidays. So if I would you I would go ahead and have a designer give you some options. You and your husband will figure out pretty quickly whether you really need to expand the bath or not. Good luck with the new house!

I forgot to add that the little rectangle next to the toilet was a cosmetic divider planter thing we ripped out when we bought the house. So thats not there - its just the toilet up against the wall.

I would take down or cover the glass block, paint the vanity and closet doorrs, replace the light fixture. get that completed then shop for shower curtain and rugs.