Norwegian have an (albeit limited) long haul network from BCN and CDG, so I imagine easyJet will partner with them like they are doing from LGW. LEVEL could be another partner from BCN, though given their links with Vueling I doubt it.
AMS, MXP and GVA will almost certainly just become easyJet euro-hubs given the lack of long haul low-cost operations from these airports.