I have three accounts and, thus, three commanders. There are very few things you can do at the same time with those. Rare trading is one where it works quite well though, even if you are piloting all three at the same time... One big ship to hold the rares, and the other two just goes in/out of station as soon as they have filled the allocation... I have done that, but... to be honest.. it becomes quite the effort IRL to manage all that.
I've also done tons of experimentation regarding the positives of doing things together in a wing, such as Mining and Trading... again, it takes a lot of effort to do it, when you simulate playing in a wing of three, but you have to manage all three boats yourself. But... I've found that most activities in Elite are favourable for wings rather than playing alone.
One thing is clear though; I will never have to call the fuel rats again.

(love those guys though... they are the best).