None of these concerns require multiple accounts. An account is a container for resources and resources do have tangible isolation between them if configured properly and properly delegated credentials should be issued to staff which are specific and limited in capability. Same with assumed roles. Same with VPC configurations.

If you didn't do that, you fucked up. Adding more accounts doesn't guarantee that you didn't fuck up.

And yes you need to open 10 tickets, even if you have enough spend to have a direct line to AWS internal staff with multiple enterprise accounts...