If a spell is exiled, it's removed from the stack and thus will not resolve
There are tons of Commander decks that focus on Auras or Equipment, and Codsworth, Handy Helper is an easy inclusion in the 99 of any of them that play white
That's probably not going to be worth most of the time, but it is funny to note that if you have two locations out with a movement cost of 1 and a Map of Treasure Planet on board, you can bounce him back and forth as many times as you want, giving him infinite Strength
It only takes a few hits with Blighted Agent when it's pumped up through any number of spells to increase its power, multiplying the number of poison counters it hands out as its power grows
There are proliferate cards available for all MTG colors
Between the counter distribution on ETB and the general benefits of being in green, we should have no trouble maintaining the largest creature