>>95938123
these are the aos models that don't have a most direct analog to a skaven unit that existed before the end times

potentially you may use the terror as an alternative hellpit abomination or brood horror
thanquol on giga boneripper as an alternative for a verminlord (as well as the various and named verminlords, there was just one)
the giant ratling could probably find use as an alternative to a warp lightning cannon
while for stormfiends you either use them as normal rat ogres (albeit somewhat larger ones) convert them into mounts for skaven heroes (the bonebreaker rat ogres) or use as unit fillers, taking the space of 4 rats with no effect other than making the unit look cool and be larger