Bases were never a problem until tax authorities started to get involved. Onshoring has caused big problems primarily because different jurisdictions have different rules and trying to comply with opposing rules is untenable for an international aviation company.
The only place where bases will open in the future is North America. When the 49ers tried to get a ruling against CX the judge rejected the claim on the basis that CX were a HK company and US jurisdiction did not extend to HK. Had the UK employment tribunal done the same with the Crofts case we would not be caught in the current tax vice between the UK and HK.
In 10 years time there will be no need for bases and most of those now on bases will either have retired or moved to HK. The bases are withering on the vine for all but the North Americans