Recurring Projects

My team has a list of projects that all have mostly the same tasks associated with them. Our setup is that the board should hold all of these in one place. We use the groups on the board for Tentative, Confirmed, Completed, and Cancelled. Items in each group would be the Project and sub-items would be the action items to be taken for that particular project. The “Start Date” at the Item level is what we see as most important as there are a list of tasks that happen prior to that start date and a list that happen after that start date.
Currently I’m using the Subitems Templates to add all of the subitems because the automations to do this are clunky.
I’d like to be able to add a new item to my top level (Tentative) then have that item auto populate subitems with due dates based on the listed Start Date at the item level.
Formulas do not work as they will only pull input from the same level and are uniform across all of the subitems. So if I’m subtracting or adding days, it applies that to all of the subitems. Dependencies don’t seem to work as they will only link to existing items or subitems and only in the same level.
Is there any way to reference data from the item level into subitems? In particular a way to automate the population of subitem dates based on the item date?