I think it would be interesting to implement "hidden" bonus conditions for bonus rewards when completing a mission. For example, +X% reward (credit, glory, influence, XP) or one extra item in the box at the end for conditions like: not using inoculator during the mission; not losing a life; not using belt/armor skills; completing in a certain time frame; killing all enemies (except Purge); saving all soldiers (Rescue); saving the VIP unharmed (Panic Room); killing all villains on the map; etc. These should only apply for missions on at least your level, so you could not farm lvl 8 missions with an lvl80 character for the bonuses. This might incite more tactical/cautios gameplay in certain situations.