One of the improvements I see for sky130.lib.spice is split of the transistor corners from the rescap (resistance/capacitance) corners. Currently if you select one of the rescap corners (ll, hh, ...) one get the tt transistor corner. Typically I have seen that these corner are split; e.g. the transistor corners tt, ff, ss, ... only enable the transistor models and the rescap corners e.g. rescap_tt, rescap_hh, rescap_ll, ... only the resistor and capacitance models. I guess this also means splitting up all.spice.