Not a good plan. It certainly can be done, but you have to make certain that the acrylic is very well bonded to the plastic surface and fully cured. That means that the surface of the model has to be absolutely clean and free of all oil, mold release agents—everything. Acrylics dry to touch quickly, but their full cure time is often longer than that for enamels.
Most people who do this sort of thing use an enamel primer and acrylics over that. I don't see the point of using both except for weathering purposes. I rarely use enamels, and I get excellent results using either Tamiya acrylics or Polly Scale acrylics as primers and top coats.
There is also a potential problem with shrinkage. Paint shrinks as it cures, and some enamels shrink more than acrylics. With the sometimes weaker bond to the substrate of acrylics, shrinkage of the enamel top coat could cause cracking and wrinkling of the acrylic primer.