Tech Familiarity instead of Tech Level

[Ashtagon]

You could just say that most WH societies are TL3, with Skaven being TL3+1(skaven) and the empire being TL3+1(Reik). Characters can then purchase TL-dependent skills at either TL3 or TL3+1(whatever). Arguably, the Reik's steam tanks are made using Engineer/TL3+2(Reik).

[Arguably, the Reik's tech is real-world default, and so should be marked as TL4 rather than TL3+1(Reik). However, since no genuine TL4+ nation exists outside of the Reik, it has the same practical effect in rules terms to call it TL3+1(Reik). IN any case, their TL5-equivalent steam tanks are certainly variant technology that would have a real-world TL5 engineer scratching his head].