Cross account API Gateway

Is there a way to use an existing API gateway on a different account and have the lambda functions be deployed on a different account all specified in a single yml file?

My manager has been bitten by the “create as many accounts as possible” bug, and wants a design with a single ingress into the accounts via an API Gateway, with the ECS services in a different account. The idea being that if an F5 or Barracuda is inserted into the mix, we would just have the one for all accounts.

The current set up has the ECS being used with Application Load Balancers, since they are able to perform the healthchecks on the application. Now this leads to a number of moving parts, and I’m trying to understand if this is even feasable as it seems like a lot of hard work, and every items ends up having a limitation preventing this. Kodi nox