Would providing this capability as a "third-party" plugin (even if the "third party" happens to be a Wireshark core developer) work? *Wireshark* doesn't offer it as a built-in capability, but you can drop in a plugin to get it.
It would not work as it is written now. At the moment it requires the plugins that want to "share" the credentials they have, to put them into the new tap I registered.
If it can be done in some other way, that's definitely an option. But I'd need to figure out how to do that without changing the dissectors. Suggestions are welcome.