I'm not calling FLStudio God's program here, but there is no need to make loop based composition unless you want to be lazy, and you can make music in the key of Z if you wanted to (I made a song that changes keys every four chords). The only thing holding you back from getting FLStudio is your dislike of piano roll (personally I prefer sheet music over piano roll, but I refuse to learn a new program after almost a year of using FLStudio).
So yeah.../useless relevant post
Slight correction. He said time signatures, not key signatures. And yes, when compared to a sequencer with built-in music notation, FL is a bit more tricky in terms of getting your changes in. Possible, but tricky.