Surge brakes aren't allowed for commercial trailers down here per dot regs....
"Any trailer with a gross vehicle weight rating (GVWR) of 12,000
pounds or less, when its GVWR does not exceed 1.75 times the GVWR of the
towing vehicle;"
However lots of non commercial trailers with surge brakes on the road. I watched a guy on a really steep boat ramp get drug backwards. The rig didn't stop till the heavy boat was mostly floating.
Many shops simply don't have the space to work on tall large vehicles.
Big rig trailer repair shops around here handle trailers of all types and sizes for that type of work...or even commercial vehicle yearly inspections.