I like Coby, because he is the embodiment of hard work. He shows you that you can become something great even if you are not the most talented. You really think his training is unbelievable? Come on man, he has work his ass off for nearly 3 years under the wing of one of the strongest guys alive. Garp is well known for his extreme training tactics, this is supported by the fact that he left Luffy alone in a jungle when he was somewhere around the age of 12.Actually Coby getting the Mera Mera No Mi fruit would be to obvious, to be honest I kind of hope that the fruit is a fake.
Coby sucks as a character not because he lost to Luffy or because he cried, he sucks because his character is a complete off panel character and we're expected to believe he will become this rival for Luffy, he's the only character I feel Oda is forcing him onto us. I hate characters like that for instance characters like Smoker who fight side by side with Luffy are likable.
His character is practically the exact same type of character as Hiroshi Miwa from Ichiban Ushiro No Daimaou (Search it up) He plays the hero who is given a suit and is somehow given the power to fight a demon lord evenly even despite how weak he is) I would honestly like Coby a lot more if it wasn't for all the unbelievable off panel training and hiding behind Garp's wing constantly.
We all know how you're a big fan of the Coby getting the Mero Mero No Mi fruit but the power of that fruit given to someone who is barely even shown in the series would be a waste.
Sure, Coby might not have the biggest role in the story right now, but it has been made pretty clear that we will become one of Luffy's main (marine) rivals. Zoro said something like that at the end of the CP9-saga.
However, I do think he needs something more to make him an Admiral before the series ends. The Mera Mera no mi would provide the perfect boost in strenght to accomplish that. It would put him roughly on the M3 level IMO.