I have a cunning plan for someone who is coveting my position, tell me if you think this is justified.......?

Tough story man, but what YOU need to do is get mentally stronger. You can't worry about what other people say to you or do in the other net. You can only worry about yourself and no one else on the team. Goalkeeper is such an individual minded position that you need to get some kind of vision that the team needs you to be strong headed. If he comes over uninvited, don't let him in. If he continues to be an ***, don't be his friend anymore. You tried to be the nice guy...if it doesn't work, it doesn't work. Having him on the team shouldn't affect you personally, and if it does, I suggest you find somehow to fix yourself mentally.