How to Restructure in Next Gen?

[Beth Duffy]

We're currently using a classic Jira project, however our implementation of it is causing severe inefficiencies that need to be corrected. With the roll-out of "New Jira", we're considering starting a brand new project to re-house all of our current issues as well as new issues moving forward. I want to make sure we structure it the correct way at the start so we don't run into the same issue. 

Our end goal is to be able to use Portfolio to schedule issues based on team. Our overall development team is split up into categories such as QA, API, UI, etc.

Right now, we are structuring things as follows:
-Epic: Overall project (ie. Create Website)
-Task (issue): step within overall project (ie. add blog to site)
-Subtask (of task): specific tasks per team (ie. ui subtask, qa subtask)

The problem we've run into is that you cannot assign separate teams to subtasks; the team has to be the same as the parent issue. This means we cannot schedule the subtasks using Portfolio based on team (which is the goal). 

How can we structure a new project using Next Gen so that the hierarchy still exists (overall project > step within project > specific task per team for each step), but also so that we can utilize Portfolio to schedule according to team? Ideally, Portfolio would be able to tell us that the API team has 80 total hours available for the week, and then assign the API specific tasks  to anyone belonging to that team.