Personally I only use a shower on a flexible hose where the handheld shower head clips into a holder or can be held in the hand. It can be used both ways--fixed to direct shower on the head or torso with both hands free or held in one hand. The overhead "rain shower" setup seems an unnecessary complication.
Does this setup have a diverter between the wall outlet and the overhead rain shower?
Contact the previous owner or the fabricator of this shower. Maybe the fabricator has contructed it so that removal is possible with much less work that it could be, e.g., maybe there are finished walls and floor on the outsides of the bench.
In the meantime, assuming the bracket of the hand-holdable shower allows it to be turned 45 deg or so (CW from above) you could relocate the rod bracket of the hand-held shower over to the left of the controls.
If necessary add an extension hose to the existing flexible connection to allow full reach, but maybe it would work as is. At this new location raise the vertical position of the bracket rod so that at its highest it is above head height of the tallest person using the shower. Current vertical position of the bracket seems too low. (Maybe the low position of the bracket is to allow washing of the feet, but this could be done with the hand-held use.)
But if you want to use the rain shower head then add a 45 deg fitting close to the ceiling and a diagonal run with another 45 down to get the rain-shower head over to where someone would be standing. A metal stabilizing support from the ceiling over the 2nd 45 (over the rain-shower head) might be required.
Alternative to removal of existing bracket of hand-holdable shower
Rather than remove and reposition the rod bracket from the back wall, it might be better to leave it in place and install a new rod bracket on the control wall to the left of the controls. If you don't need a long adjustment range you could get a short rod so that both ends could be located above the decorative band perhaps within the same piece of 18" tile. The grab bar which attaches with special adhesive would allow attachment without drilling holes if you wanted to avoid that. However, it is very likely that there is no plumbing in that location so holes for anchors would probably have no interference.
Grab bar without drilling. These were developed for installing grab bars to glass, stone or tile. The can be reportedly be removed with no damage to the original wall and no trace they were ever there. I have never used them because I drill and use anchors, have basic soft white small tiles and I would tolerate filled holes should I want to remove the grab bar later.
I can imagine cases where drilling was not wanted. These adhesive attachment bars could be installed without drilling by following the instructions. This bracket bar should have very little stress on it, but of course if someone felt they were about to fall this bar would make a handy grab bar.
Alternative use for the raised bench
Perhaps best not to remove this bench. It might be useful for washing a dog or certain other washing jobs. Maybe fully able persons would find sitting on the edge of the bench beneficial. Since it is already there see if it is useful.
Long vertical grab bar to the left of the controls
Alternatively you could mount a long grab bar (matching the other in appearance) vertically to the left of the controls. The bottom end would be well below the decorative band and the top end as high as necessary to act as a mounting for a bracket to hold the hand-holdable shower head. You could have a bracket fabricate that would clamp to this grab bar which would give an uncluttered appearance and unobstructed access to the grab bar. I can imagine holding onto this with the left hand while reaching for the water controls with the right hand.
Personally I would drill into the tile and use anchors for the ss screws which come with these bars (two needed on each end). Alternatively, there is an anchor called a Wingit which fits through a single 3/4" hole on each end and is very secure. If there would happen to be a vertical 2x4 at the location or horizontal blocking, the two ss screws into that are all that would be needed.
If there is a cavity there, then the recommendations are to use a Wingit or other similar anchor. Personally I have found plastic anchors work as well as needed (in my thick bathroom walls: tile, 1/2" cement board, maybe drywall under that) and these use the supplied ss screws. Not everyone agrees that the plastic anchors are adequate for a grab bar. I use two anchors on each end into each 3/8" dia or 5/16" holes all the way through to the cavity. Could depend on what is under the tile--minimal cement board or something heavier. There msut bea reason why the Wingit is recommended.
Alternatively, the original type of rod could be affixed to this vertical grab bar and that rod used to adjust the height of the shower head. In that case I would avoid drilling into the grab bar to secure the bracket rod because that would be a route for water into the inside of the grab bar.
After-shower dripping from rain-shower head
These seem to be more prone to dripping than the standard shower head. One procedure that might eliminate this would be to turn the diverter to an intermediate position after showering. In this position the rain-shower piping can drain back through the lower piping of the hand held shower.
If this doesn't work as well as desired, then also take the hand-holdable shower off its bracket, drape the flexible hose over the bench with the hand holdable end hanging over to drain all this tubing more fully. It could be left in that position till the next shower, but in case this seems unkempt, let is sit there for a few minutes before replacing it on its bracket.
