This is exactly the intention and why the library calls are provided the way they are. There’s no fundamental difference between a single phase UK setup, a split-phase N.American setup and a 3-phase UK or elsewhere setup, as far as the emonLibDB library is concerned, they’re handled most of the time as one, two or three single-phase channels. With a 3-phase emonVs and two or three phases, you can specify the line-line voltage rather than the (implied) line-neutral voltage.
So to the library (I had no control over the sketches that have been uploaded or appear on Github) all you suggest is catered for.
However, I would suggest adding a 180° phase “error” is a bad idea, far better to use a negative amplitude calibration or point the c.t. in the other direction.
I suggest you download and look at the emonLibDB documentation published on this forum.