Hello Bodhisattwa

I'm not convinced Montage should be the communications platform for the jurors. Actually, I think that having each juror point the images independently at first is a good thing, as it avoids potential bias based on other jurors points.
Seems that your national competition used a direct output of the top-10 images as rated by every juror combined, rather than e.g. take the resulting top-20 and then have the jurors discuss the merits of each one to make them into a top-10.

Finally, I am a bit concerned about your scenario of a jury member which «does not want to join calls or does not want to communicate through other private channels» and «so that communication does not depend on the will of organizing team or jury team members.». If a jury member reject to communicate with other jury members, that's a social problem, not a technical one.
You could make it easier to find all the tools needed (such as adding a link to the mailing list from montage), and it can be quite hard to get a suitable time to get everyone online. In that case asynchronous communication (like mailing lists) may be needed. But ultimately, your jury members should be willing to communicate with each other. And the expectation of that they should do so, and may need to perhaps join X online meetings, should be clear from the start.

What makes you think that someone who refused communicating with other members would however be willing to communicate with them if done through montage?

Cheers