the drawback is that Luffy doesn't know he has a god fruit, so while Luffy in theory could do anything, because he believes he has the rubber fruit, the Nika fruit will only act as if it were the rubber fruit as it has been for the last 1000 chapters.
That's why Luffy turns the ground to rubber. Because he thinks he has a paramecia and were his fruit actually the gomu gomu no mi, awakening would have allowed him to turn the ground to rubber.