This is a shower for somebody who walks, in a house they intend to stay in. It does not need to look like a hospital, and most of what matters is invisible once the tile is on. The distinction worth getting right is between what has to be built into the walls now and what can be added later, because those are wildly different costs and people routinely have them the wrong way round.
Blocking is the whole argument. A continuous run of solid timber or 19mm plywood fixed across the studs from roughly 750 to 1,200mm above the floor, on every wall of the shower and beside the entry, means a grab bar can later be fixed anywhere in that band, at any angle, by anybody. It costs a sheet of plywood and an hour while the walls are open. Without it, a bar goes into tile and drywall on plastic anchors. Adding real blocking afterwards means taking a tiled wall apart.
Seating, controls and water temperature come next. A fold-down wall seat needs blocking of its own; a built bench is permanent, around 450mm high and 400mm deep, and it takes that depth out of the shower. A handheld on a slide bar works seated or standing, though the bar itself is not a grab bar unless it was specified as one — and it is very frequently used as one. A thermostatic or pressure-balancing valve with its maximum temperature stop set keeps a flush elsewhere in the house from producing a scald.
Two things get left out, and both are cheap. Light: an even, brighter level inside the shower rather than one fitting in the middle of the ceiling behind you. And contrast: a floor and a wall in the same tone make the edge of the shower effectively invisible to an older eye, so a tonal step between them does more for safety than most fittings. A matte, small-format floor tile adds grip through its joints.