Based on this Aha Page, Advanced Estimates can only be added to Initiatives, Epics, and Features/Activities. In our environment, we need to identify team impact early on at the Idea level. These not work requests, but rather an identification of which teams we think will need to do work so we can estimate total cost by team before approving ideas. As such we would like to have this feature available for Ideas, and in particular there is currently no workaround (i.e., cannot create custom fields as a relationship with Teams).