Hi Dai,There already is a real purpose made swivel out there, I have actually used it Its called.....................The SideWinderOnly problem is it weighs more than the brush!
Hoseless wfp system
For me it would be a brush with a good bird muck remover.Oh' and a really good swivel, I am still using the Stanley paint pad swivel that I converted and it works very well, but I would have thought some manufacturer would have come up with a purpose made swivel by now.