One thing I'm wondering. Can't Billy just copy Unluck?

Was very nice seeing Gina again though. Even in flashbacks best girl remains best girl
my speculation on why billy didnt just copy unluck:
1. Billy copy power seems weaker than their original. even tho Billy used undead to stop Spoil/rot, but its still look much worse than when andy got one. I think this is billy's power limitation. cant full copy 100%
2. Billy cant upgrade the copy power to the fullest potential. If original user's power grow over time, its not apply to billy. Juiz said to billy this chapter, 'you still had undead
left on you, right? so.....' So billy cant access like Victors Undead power or whatever Unluck fullest potential will be..
3. Another Billy's power limitation is he need the original owner to 'not believe in him'. we know fuuko character, the 2nd time they met, billy will no longer cant used unluck, like Unjustice did..
4. unluck limitation/drawback depend on LIKEABILITY of the user to target. Its best suit for Fuuko's character. I doubt billy had same heart. He may/may not evil, but he is not easily trust and like others.
so yeah, in the end, it will be useless. So you need the original owner to get the power, fuuko itself..