I understand what you are saying, been cleaning brick, concrete and other surfaces for over 20 years, over 8 years with my own company. Brick and concrete usually need pressure to clean as it is dirt that will not chemically clean where the mold, mildew and algae will clean up with chemicals so I know what you are talking about.
I just got rid of the last of my graffiti chemicals, the city has 2 trucks that clean it for free.
When I cleaned graffiti whether standing on the ground, up on a lift or on scaffolding, I would apply the cleaner, give it some dwell time and position the elevated support back further so I could use the longer wands and not get soaked, some of those graffiti chemicals are very bad for your skin.
I would use the scaffolds with the wheels so that I could lift up the end and move them but I would position them so that the narrow side was close to the wall and you could walk back further if needed. You still have a wand cleaning width of anywhere of 6' to almost 15' wide with the right length of wand going side to side. The further back you are, the less likely you are to get soaked. The pressure and gpm's will really not change when using a longer wand at the end of the gun.