ORIGINAL: the troll
Work with the other club and work out the arrangements to allow safe flight. The new club may need to be made aware that their actions may be construed as reckless or negligent if they refuse to participate in a fair arrangement to allow safe operation at either site. The original club does have a position that may be successfully defended if need be.
Agree with most of your your points, but don't understand these. Who except for members of the adjacent club would construe the actions of members of the new club as negligent, if they failed to reach agreement (freq sharing in particular) with the club that was there first? By what legal theory does the original club have a preferential position that can be defended?
Abe