In Search of a Solution to Assign Tasks to Users Without Giving Them Access to a Team

Hello all, 

One of our users has an interesting use case where they would like to assign tasks to specific users either without giving the user assigned the task access to a team or possibly removing their access automatically once the task has been marked complete.  What would be the most seamless way of accomplishing this?  I know that using Planner one can assign a task to a user not currently a member of a team but this would therefore make said user a member and leave the responsibility of managing group membership to the group owner.  

Power Automate seems to be a step in the right direction but it'd be preferable for the group owner/task assigner not to have to worry about this overhead.

Are there any alternatives?

E: Forgot to mention that these tasks will be assigned at will so dynamic group membership would not be suitable either.

Thank you!