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It would help the sense of progression if the links between missions were constrained a little, to give us a more purposeful progression through each planet, so yeah, I agree, that'd be a good way to do it.
As for your sidebar Idea, that's great, honestly the party interface is just outright bad, they need a party bar, that's all easier an in the one place, I can click a + sign to add a friend or press esc to then hover over my name to leave a party, all of it should be in the one accessible place.
To assign a Gear to a slot, highlight and select the slot on the wheel and then select the Gear you want to assign to that slot from the Gear selection window.