Ability to send "Once in a lifetime" Outreaches based on Email Address only

Currently when setting "Once in a lifetime" in Outreaches, the logic enforces uniqueness across Email Address + Account Id.  This is the desired behavior for most of our use cases but we do have some user cases where we want to send to a contact only once on Email Address only.  So if that Outreach went to send for a different Account Id it wouldn't because it already sent that Outreach to that email address for a different Account Id.

Below are a couple example use cases:

Use Case #1: Once in a Lifetime Partner communications - We have communications that we want to send to partners only the first time that they hit a process with one of their channel deals.  So for example we would introduce them to the Renewal Process when their first channel comes up for renewal.  We have partners that manage dozens of channels so we are not able to implement this with Gainsight without getting creative like adding a field to note that we have sent a specific email to them.

Use Case #2: Low Touch New User Welcome email - These emails serves to introduce a new user to our product and provide links to resources like training, communities, etc.  Even though we have Once in Lifetime selected currently we see these emails go out to the same email address within days of each other when they get added to two Accounts at the same time.