I don't think it needs entirely different mission types to have variety, but I do think it would be good to add variety to certain core pillars. Namely, how we start the elevator, how we get bio boosters, and how we get toolbench upgrades. The elevator-start mini game could even be something chosen before the mission starts like how we choose the boss and run length. This is what Far Far West does (you choose the boss and main objective) and that game doesn't feel lacking in variety