Currently, no easy way to change. SEA-CDG award availability has been terrible on the days I need. Even Expert Flyer hasn't found me a good option (6 months and counting).

And, confession, I am kinda excited about flying mini-cabin business on AA 50 to LHR.

AA has said that they will likely be able to check baggage all the way through on BA flight. AA 50 has 71% on-time arrival with avg delay = 16 minutes.

I will likely role the dice that I can get from T3 to T5 in a timely fashion and end up in wonderful Paris with an afternoon in front of me.

I'll let you know how this pipe dream turns out.