You overcome it by offering something valuable for users that they can't easily setup themselves.Why can't traditional IRC services be used for this? I'll preemptively counter the end-user configuration side of this by saying it's increasingly easier in a managed workstation environment to deploy images with software required for that worker's tasks preconfigured. Even in a non-managed environment, an IT staff willing to build the packages and make the configuration edits can make accessible an installation candidate stored for access in an infrastructure library so users can save (after proper credentialing and auth checks have been satisfied), install and login.
Security, perhaps? That's always a valid concern to have, but if that's the case I would hope that an adequately planned and designed audit of any service not being managed internally gets the same look. Corollary: perhaps one should not be using anything not managed internally for sensitive matters to begin with; collaboration and non-secure communication where a failure of this system wont halt production or cause the company to incur significant loss however are par.
If I'm off base here, I'm willing to discuss it further. While I loved IT, I had to run for the door after getting burned on multiple opportunities to manage programs and create user friendly but secure policies. And by burned I mean hired to do exactly that, only to end up in hyper-glorified purchasing support roles. shudders