Most of the time people want to forget what happened to their team before their arrival.
You also can see quite easily if the name has been changed during the season (so change of user) or during the offseason (choice of user).
But if you can find an esthetic way to show these information, an easy way to implement it and and an extended time for the devellopers, why not.
It is easy - there are two colors used on this page - one for the past, and one for the presence.
All information which is in black is related to the current user.
The gray colored information is part of older users.
Use the same scheme to identify ANY user change.
It can also be done with only two colors as well.
Regarding the developers time;
I'm not their manager. The priority of the tasks will be defined by him.
The need (and this is a low priority, but easy to implement feature) and the difficulty of implementation (to some degree) is what is can be discussed on this forums.