I added one new function: makeSkyWcs(pixelsToFieldAngle, orientation, flipX, crval, projection="TAN") rather than the two requested functions. I did this because it is not enough to have the IWC to sky transform, one must also construct an appropriate ast::SkyFrame with the SkyRef and SkyRefIs properties set, and I wanted to avoid users having to deal with that or with FrameDicts.
Note that "orientation" is with respect to the focal plane, not CCD x, y. This can be helpful for cameras such as HSC that have a mix of CCD rotations, because the same angle can be used for all CCDs. However, it does require some care on the part of the user.