I personally like a hand-shower with a long lead ( with overhead shower combo) but that might be because I have two dogs. :) Previously we had one of those big square overheads, and I'd definitely have one again. Although ours was a cheap LED-lit one we bought off eBay (don't do this - the LED's do not last, as we learnt twice) it was good for getting you drenched (for soaping or unsoaping) - the water didn't shoot out, it was just a rainfall across it's square-footage. Our current one is just your standard, basic, shower-head on a marginally adjustable arm. It's not the same.

diverter tap would work best so that when you turn on the shower the water is adjusted for temp, when you want the over head just switch it over, in my experience most women don't like overhead showers

(black wire?) shelf on the empty wall will will hold more, drain better and be cleaner than soap build up in the niche ...btw is there enough space to have the toilet next to the vanity and have the shower wall to wall with the taps on the end wall and niche or shelves in place of the "white box"?

I had one years ago and just accepted it's what was there. My preference would be to have at least a shower but if resale is on the cards then I think both seperate if possible unless there isn't room. @macyjean, the tap is away from the shower, it will be the single tap you can see on the bath wall under the hob that will have a tripple function, shower, hand shower or bath as in new builds at least I believe it's mandatory that the shower taps are out of the shower zone so the water temp can be adjusted first. If you look closely there are no taps on the shower rail. Your suggestion of a grab rail is a great idea but hard to know where it could be put but perhaps there is a spot on the other end of the bath??