I think it'd make more sense just to start/terminate the Barrows/Windermeres at Preston or even Lancaster and keep two Blackpools. That way you not only remove a train from Castlefield but also a DMU from under the wires.
And like a broken record, here we go again!
While it may make sense to people who play with train sets, it wouldn't make sense to international passengers from/to the advanced manufacturing sites in Furness nor to passengers who come from the expanding international tourism market to Lakeland.
The former market, in particular, is only just starting to recover from the extensive service failures during the previous and current franchised, some of which continue intermittently at seekends and the temporary but longstanding withdrawal of many through airport services on the Furness and Lakes Lines.
Regular observation of passengers with large luggage, especially southbound, changing at Oxenholme and Lancaster onto frequently very busy TPE services might temper your view.
Heaven perish the thought that passenger convenience should be a factor in running train services...