I think required landing distance is the deal breaker for 738 operations at SEN. I looked at the performance charts some time ago and it looked as if it was not possible to fly an economical payload into SEN. Earlier this year Luxair operated two full rugby charter flights from SEN to Pau but significantly the inbound pax had been flown into LTN.
I cannot really see Jet2 setting up a base at SEN with 733s as they will surely be retired within 3 or 4 years I would think. The 752 could operate effectively from SEN, although this has never happened yet, and although that would be very nice to see I doubt that Jet2 will do so either.