Change Class button on queue pop
Replaces the 'Join' button with 'Change Class' when your class is different from what you queued up with. Clicking the button would show a drop-down list with any gear set you have for that class, with sets under the required item level being greyed out. Selecting a gear set switches to it and confirms your participation.
Clickable notification when friend/FC member joins Duty Finder
A small, fading notification (maybe 5 seconds default, changeable in settings; moveable) to notify you when someone in your social circle joins Duty Finder, what they queued up for, and what roles their party needs. Clicking the notification brings up a window with your classes, with the filled roles being greyed out. When selecting a class, a drop-down list of that classes gear sets appears, with sets lacking the required item level being greyed out. Selecting a set automatically merges you into the party & queue as the selected class/gear set (without changing your current class/gear set).
Checkboxes in the duty finder to make your party Open, By Request (showed in the notification), or Closed (no notification) would alleviate unwanted joining and requests, as well as those joining lowering the party's base item level/duty eligibility.
Options to turn on/off notifications for friends/FC as well as Novice Network/linkshells/nearby, or disabling the feature completely.
Clickable notification when current class is 'Adventurer in Need' role
Similar in function to the previous suggestion, but appears when your current class is a role in need. Separate notifications appear for each roulette. Clicking a notification brings up a window showing the gear sets you have for your current class, with sets below any item level requirements being greyed out.
Options to change fadeout time, as well as disabling the feature for specific roulettes/classes/gear sets, or disabling the feature entirely.