API changes to support line items on civicrm_contribution_recur records

Eileen, can you help determine if any changes are required to the api to support some new functionality?

We are looking to support line items being edited for recurring contributions. The approach is to create line items that point to the contribution_recur record. These line items represent the next contribution's line items, and will be editable. When a new recurrence of the contribution series occurs, instead of copying the most recent contribution's line items, the line items pointing to contribution_recur record will be copied.

Currently, as I understand it, the way to create a recurring contribution via api to:
1) create contribution_recur record
2) create contribution record for first instance of recurrence passing contribution_recur.id
3) create line_item(s) passing entity_table='contribution' and entity_id=contribution.id

I think that all that is required going forward is to add 4) (ideally between 1) and 2)):
4) create line_item(s) passing entity_table='contribution_recur' and entity_id=contribution_recur.id

As a result, there is no need to modify the api.

However, this is the kind of business transaction that should ideally all be supported by a single API call, so that, for example, we can ensure that all of the inserts are within a mysql transaction.

Can you let us know here if there is work we should do for v4 api call for contribution_recur?