Luffy ate his first devil fruit more or less just because he was hungry, it's shown that he is a very gluttonous and will eat anything you put before him. I know it's been theorized before that Monet's snow fruit reincarnated on the orange trees on the sunny.

I believe Luffy will be the first character we see eat two devil fruits. I do not mean gain the power of two as Blackbeard has done, but to actually physically eat two. With the Nika fruit, and the snow fruit. I do not think he will gain powers from this, and may even suffer greatly, possibly coming close to dying, with chopper keeping them alive.

I think that it's possible during this that Luffy could have some sort of spiritual-esque journey, seeing the events of the previous holder of the Nika fruit and snow fruit, giving us a flashback of the void century which will end with Luffy deciding not to continue the cycle of inheriting will, by completing Joyboy's will. Presumably the snow fruit would be expelled from his body, and result in Luffy understanding the grander issues of the world, and for once be the person leading a revolution, instead of just helping with one.

Is this stupid? Maybe. Is it right? Almost certainly not. Is it interesting and something I'd like to see happen? Hell yes.