I think option 3 is not a good one. The others are potentially okay.

I'd be a bit careful with 1, 2 and 4 - there was a report on the BA board earlier this week of a BA telephone rep telling a customer that if they skipped the last leg of an ex-EU booking, BA would look to retroactively reprice the ticket and collect the difference. Obviously that's BA and not CX, and it sounds like a legal minefield, but perhaps worth bearing in mind.