I'd ask your client why they would want such a requirement. RConJ does have the Sync button which, when not selected does allow users of RConJ to switch screens without affecting others connected using RConJ, but it is not foolproof and in my opinion multiple remote connections to the server at any one time should be avoided to stop the server having issues. There is also the security of the server you have to consider here, not physically of course but remotely because a user with Remote access can take the thing down if they don't know what they are doing.
For example, many moons ago someone I was working with typed "EXIT" at the console of a NetWare 4.11 server thinking he was in a DOS window when infact he was in a RConsole session. The server quite rightly told him that he had to down the server before he could exit, which he did affecting 300+ users.....
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"It's true, its damn true!"
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