In Lync (Skype for Business) it was possible to create an XML file with a registry key edit and add up to four custom presence messages with a flag to set the "status light" to the correct color if busy or away. If a user were then engaged in a mobile call they could manually change their presence to say "In a call" even though Lync wasn't the method used for the call.
I would like to see Teams with a supported option to create up to four custom presence messages. Many in the forum have expressed a desire to have a presence indicating they are in a mobile call instead of just "In a call", a presence such as "Be right back" as in Lync, or others such as:
"In a remote support session"
"In a web conference"
"In a conference call"
"Presenting"
"Out for lunch"

Permitting a user-defined custom presence would allow MS to keep the basic presence types while empowering users to customize their own to better fit their situation.