Currently we don't support filtering team but support filtering team members. So I suppose that a workaround you could do is to add all the members in one team, and group them by different roles corresponding to their teams, and when assign the task, find that group by a field role value. 

For example, if you have 4 teams, create a new team containing all the team members across all 4 teams. Then according to each member's previous team, group them into four groups by different roles. Use a dropdown field which contains the list of all roles (use a database lookup) which previous submitter belongs to. Then you can choose the newly created team (which contains all the people across all 4 previous teams), and use "filter " ($result=team.findMembersByRole($util.getValue('Single_Line')), where "Single_Line" is the field contains the selected role.) to assign the task to the members under that role (i.e., the same as one of previous 4 teams).

Basically the same idea as your team field idea, but use the roles to group the data instead since dynamically assign tasks to a team is not supported yet. Hope this helps.