I would also find this beneficial. I don't have a large number of users to support like you, Ciag, but centralised authentication is definitely a high priority for us. TACACS+ (or Radius... but preferably TACACS+) integration would be ideal, though AD integration would suffice. The justification for using TACACS+ rather than AD directly would be to avoid duplication of effort with configuring access rights and so on for different users/groups. The more places where you have to set up access rights like this increases the chance you're going to forget to add or remove something for a new starter, or a leaver.
No idea how you'd achieve this, but it would be lovely to *optionally* (i.e. in addition to current options, not in replacement of) use the logged-in users' credentials for running command scripts etc. rather than the global credentials for certain devices, to make auditing more straight-forward. I say 'certain devices' because not all of the kit in our inventory supports Remote Authentication such as TACACS+ or Radius..
Hang tight guys - I think you're going to be pleased with some things that are on the road map and coming up soon.