I probably wouldn't recommend no showing on the outbound leg in case the return was cancelled but what can they do on a return leg? Especially if you OLCI so the first they know is at gate closing.

To add some further info on situation 2, J availability opened up a couple of days before return leg so I called up BAEC to ask if I could cancel 241 booking and make a new standalone J redemption for my wife. I ended up (thankfully) speaking to an excellent agent in Manchester who reminded me that you can't cancel a redemption once the outbound is flown but she could upgrade the 241 to J for £70 & the extra avios which was actually a lot cheaper than my initial plan. She was aware that only 1 person would be flying... We didn't procede in the end as my wife didn't want to "borrow" the extra Avios from her friend but I was pleasantly surprised at how creative her suggested solution was.