I like G5 design. Adding touch of looney toon is fine as well and sometimes it is funny.
With G5 abilities, oda has definitely open the box of new ideas and creativity he can incorporate in Luffy's fighting style.
My only issue is Luffy's constant laughing and non seriousness. It takes tension away and tones down the gravity of the situation.
Imagine we are watching the anime - two top tiers are trying to kill VP and sanji is struggling to run away from there with VP, suddenly kiz laser hits VP and he dies ..*sad background music plays*
Then, in next scene you have Nika who is standing close to VP and is an ally laughing like crazy