I'm not sure if that would be possible. You can make a quick link from the browser while in the workspace. Hit your browsers "..." settings and there should be "Add to homescreen" or some variant of that. This could atleast give you a quick way to jump back into a workspace from your phone. Depending on the OS it will even show as its own application on the device so you can see it in your recent apps too.

Side note: Workspace doesn't use XMPP like the chat features of SmarterMail otherwise an XMPP iOS or Android app would work well. If you did want chatting in groups could turn XMPP on and use aliases as group messages? We used to do this in house.