Scenario:

Planning a summer return trip LAX-FRA. Outbound date is certain and there is a decent F Basic Plus fare available. The return is uncertain. I can pick a likely return date (50% probability) but a lot can happen between now and then and I may stay much longer. I’d like to lock the outbound in and need to pick a return to get the F fare. I’m picking the likely return date in Business Flexible (not much more than Business Basic) to have flexibility. In case my return plans change I can either rebook if the fare difference is not too much or - my preferred solution - cancel the return and use miles for a business award ticket if available (likely at that time).

Question:

If I book the restricted outbound and the flexible return and take the outbound flight, can I simply cancel the return and get a full refund on the return portion of the original ticket (LH prices outbound and return separately when booking, so it seems clear what the refund should be)? Or is there something deep down in the fare rules that prevents this? I suspect this may be the case since otherwise people could just book a restricted outbound/flexible return to effectively get a one-way at a much lower fare.