You seem to have something mistaken - you don't need to open ports on the local machine to connect to a remote system. ie. you don't need port 23 open locally in order to connect to a telnet server elsewhere. Is this a peer-to-peer system or just a standard client-server one? If these people have firewalls that block outgoing connections based on destination port, then telling them to allow connections to those ports (which is not really 'opening' them) constitutes virtually no security risk whatsoever.
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