One of the best things about BA is the ability to mix fleets.
Done 4/5 years SH? Try LH for 4 years knowing that you can constantly bid back to SH in the other seat if you don't like it. That ability is worth its weight in gold when you like variety as it allows you the chance to move fleets without moving company.
787 as mixed fleet SH and LH? Who knows hopefully yes and see a return to the nice mixed fleet of the 757/787.
Good luck.