For 5* characters, I think you are best off picking a classic you want to fully cover rather than one of the ones in latest legends. If you're planning to cover multiple characters in the latest pool, you've got no idea which you'll get most covers for.
Alternatively, if you were planning to pull until you cover the oldest latest character and then stop, it could make sense to favourite that character. It would make sense to carefully track your progress towards the next cover so you don't end up with marooned shards. You'd need to watch this as you open tokens rather than counting how many you open due to the chance of receiving bonus shards. Also, don't exchange the shards for covers until you're finished, to give maximum flexibility.