Would these champions make use of; or is it abuse cases if these champions use cotc?

I've been wondering about champions like who either go full bursty ap, which they take thunderlords, then theres the dianas that do items like etc. as a Courage of the colossus user, she goes from a burst mage style to an ap bruiser/fighter with more survivability granted to her kit.

The same can go for who can also do something similar with style items to get the keystone and still do his diver style of play.