The above strategy may not work in the future with the type change on the pax fleet from 744 to 777.
I think that it is technically possible though to upgrade to command on a base on the pax fleet and may be easier once it is a twin which is normally the only type you can upgrade on (whilst on the pax fleet)
That said there may be some base protection and a type change allowed (there is always the joker, a one off type request) if you upgrade to freighter command particularly in the light of a shortage of applicants.
In other words I think it is entirely possible to stay on the base if you are prepared to wait.
js