If it dilutes the quantity and quality of flying in an existing base without the contractual provisions of a new Base (such as you mention), it does indeed abrogate seniority. If there's enough flying in a particular city, open a base and allow people to bid into it per the seniority list. For example, hundreds (if not thousands) of pilots have chosen to live, at great expense, within driving distance of SFO. Now, open a "virtual base" in Portland Oregon; the trip pool in SFO diminishes and negatively impacts the livelihood / QOL of the person living in California at the expense of the commuters that now enjoy a lower cost of living AND the ability to drive to work.