With mine we created a wooden frame in the opening, and the panel has cabinet magnets to hold it on. When we need access we simply prize the front off, no screws needed. See pic.

Did you find a shower door / panel to fit? Sommer have a 760mm (pivot) door and side panel (700 - 900mm) available. All 8mm thick: https://www.wetrooms-online.com/wet-rooms-online-store/wet-room-shower-screens-enclosures/sommer-8-shower-enclosures-doors/sommer-8-wet-room-shower-enclosure-pivot-door-side-panel-760mm-493-detail.html

Could you make a feature with that end section and but the wooden strips diagonally? I've seen a photo of these been done but I cannot find it anywhere. You could then maybe use that are your feature area with a lovely floor standing mirror and a big plant or some other things you want to stand out in that corner. I think you can make an amazing feature from your mistake.... be not disheartened!!!

We re-did our family bathroom last year and have a shower over the bath with a glass screen. We went for quite a simple square ish design of bath - so it gives plenty of room for showering. My only top tip - go for a simple bath screen with the least amount of fittings / hinges and slidey bits because they’re all a pain to clean!!! Our old (and expensive) screen was a sliding one and we could never get to certain bits of it, and within a year or so it looked dreadful. The new one was much cheaper and is a simple screen that folds both in and out. It also has one long hinge / wall attachment - so it’s really easy to clean. A year in and it still looks like new! The other thing we did was to have all the shower fittings concealed in the wall - again makes cleaning easier. And we also ditched the taps and went for a bath filler that is controlled by the shower fitting. Again - we chose everything with a view to be easy to clean!!