This product is a detailing product, but works extremely well in a ss bay at 128:1 - 64:1.
http://www.chemicalguys.com/Car_Wash_Bug_and_Tar_Remover_p/cws_104.htm
Of course, at $18 per gallon, it is pricey, but you can get a savings with a bulk shipment. Also, it is a seasonal product, so you don't have to run it all year long.
This is very concentrated and can be diluted down to suit your needs. Like I said, 1-2 oz. per gallon and 30 seconds of dwell and the bugs come off with the hp and/or foam brush. It will actually remove tar at full strength and will not damage the finish, so you can see its potential.
This is safe and is not D.O.T. regulated, so no concerns there. I wouldn't dip my hands in the concentrate, but there is no corrosive shipping or handling labels. It is certainly safe in the concentration that goes out to your bays.
I never thought of mixing products (don't know if contamination would occur), but you might be able to mix this with your current presoak, like MEP001 said.
Mike