Dual Sim / home and travel Sims / disable cellular on home plan / wifi calling enabled for home plan

When will Apple allow disabling cellular and data for one service plan but still allowing wifi calling for the same plan (like airplane mode with wifi enabled). This needs to be per activated sim. This way you can travel to another country, use a local SIM card plan and have your home eSIM taking Wifi calls when on Wifi. Without this function I still need to carry two physical phones (annoying).