The T1 airlines may agree to bussing in order to stay and expand in T1. Jet2 had a number of remote stands over by T2 this year. As did Ezy in the summer peak.
There’s an argument that Jet2 could be the ideal airline to move. They use very few contact stands at T1 so being in T2 for check in and arriving pax wouldn’t mean much of a change to the stand plan.