Great topic, but 25m is too much, my first thought was to go HUGE but I have no idea about commercial / industrial size filtration and maintenance, so the next option is to scale it down and go for a feature tank.
my idea would be for a tank in the entrance lobby of my big new custom house (paid for with my 25m) a staircase would run up both sides and along the back giving views of all sides and multiple
levels. perhaps a bridge style link so it is viewable from another room.
This is what I was thinking, you can’t see the link to the room at the back in this photo, the tank would be 360 viewable and I would have some comfy chairs round the back to sit and stair for hours.