Well to start, i'm not a developper or something xD I know really nothing about java or something... 
I'm just a player  
  
About the leader channel, i'd keep it only for leaders.. simple reason will be spam. 
Should be a channel where leaders can organize their fights, no need for party members to be involved. 
could be viewable by members.. doesnt really matter 
  
About the main assist.. don't do that 
I'll give you an example > 
We run a party with 2x bishop, 1x tank, 1x OL, 5x archer 
  
Bishops will have their targets inside the party (not on the enemies ofcourse) 
Tank need their target on for example the enemy's bishop 
OL doesn't even need a target, unless the sleeps/fears somebody 
So main assist is only for the damage dealers... if you'd change the whole party's target it will fcked up xD 
  
So i think you can best work with just a text message or something when the main assist changes target or if possible some kind of mark on the enemy 
  
About the gear, yes.. basicly just take the code from somebody else (i think Falcon? or LeLouch wrote it before...) 
Just a nice extra :) 
  
Wouldn't do the party matching... nobody uses it on later clients, so wouldnt add it on interlude to be honest :p