evigweight does not offer an automatic way to deal with gaps, dead/hot pixels and columns in the detector.
An easy and simple approach is to assume that the source in the extracted region emits homogeneously. In this case one can directly compute the BACKSCAL keyword and add it to the spectral file via backscale. For images one may get the corresponding exposure map via eexpmap, switching off all the vignetting corrections (mirror, filter, quantum efficiency) in eexpmap except the gaps and bad pixels. This is done by calling eexpmap with withvignetting=N and withpatterns=N.