Feature request: speed setting for first structure layer on support layer

I'm printing an object that is almost completely supported by PLA support layers before the actual ABS structure layer starts. I'm having major problems with the adhesion of the first ABS layer on the PLA structure. I played a lot with the support material shape and gap, but finally learned that this was caused by the printing speed. Reducing the speed for that layer solved the adhesion problems.

Slic3r has an option to reduce the print speed for the very first layer on the print bed, with the purpose to enhance the adhesion of that layer. To solve my problem, I would very much like the option to reduce the print speed also for the first structure material that is printed on a support layer.

Bottom side of the object, which clearly shows the amount of support material:


Top side of the object.