The current business model is primarily Mediterranean Leisure with a few city breaks. It doesn't matter how many Ryanair management join Jet2, it won't make Brits go on holiday when there is no sunshine and cold weather in the Med. Therefore the winters will always be quieter for obvious reasons. But yes, there is a need to increase revenue in the winter to pay off the new aircraft as quickly as possible so now the major bases will be flying 6 days a month instead of 3, which is still a nice balance.
I very much doubt the airline will go back to its LoCo roots and try to take on FR and EZY.