I doubt that an additional chord would be provided, at great expense, to allow WCML services to call at Carnforth! If anything, reinstatement of the mainline platforms should suffice - I wouldn't have thought it'd be necessary to recess 100mph passenger trains to allow a relatively infrequent express service to overtake, given the short distance between Oxenholme and Lancaster (and the 8 minutes minimum that'd be put into the train being overtaken...!). Personally I think it's important to make the most of these rural interchanges, but there's no point providing the platforms if no-one's willing or able to make the connections work.
As for intercity trains calling at smaller intermediate stations, that's unfortunately going to be inevitable in some cases in otherwise sparsely populated areas, where those intermediate communities aren't sufficiently large to support an additional stopping service.