Inductors are one thing, common in RF CMOS. Transformers
are another entirely. Does the foundry, whose PDK you're
using, offer baluns under any kind of relationship? At all?
You're complaining about not being given every device you
could want. To me it looks more like industry-normal, the
inductor library may simply not include transformers let
alone variable ones. I've seen a few RF PDKs and none of
them had a balun. The closest I got, last place I worked,
was a paper from somewhere else that the CAD manager
handed to me and said "good luck".