That would blow up the planet! lol
If Naruto added wind, I believe so; thus making him the child of destiny. (jk)
1.) Nature chakra clone - not that interesting I suppose. But there are so many clones out there besides shadow. I don't just mean a shadow clone with part nature chakra, just nature chakra in it. Why use it? There's an infinite amount of nature chakra, while even Naruto can get exhausted from using too many shadow clones.
2.) Nature chakra Rasengan - this would not be like Jiraiya's where sage mode made his Rasengan better, rather this one is made of pure Nature chakra. I have no idea if it's better though.
I've been trying to think how Naruto could gain access to those combination jutsu only available in "fusion mode."
3.) I suppose that he could make some nice combinations with Gamabunta and Kichi. Using sage mode, he's go an infinite amount of chakra, so it's not like summoning's are chakra limited now. Give Naruto a summnoing tattoo on his wrist for the toad stomach, and it becomes a near instant ultimate defense. Sure Ameratsu can burn through, but he can just summon another part.
4.) Automatic genjutsu break. Genjutsu works by the opponent controlling the user's chakra. This is fine except that in Sage mode, Naruto is constantly mixing his chakra with the Nature chakra, which the opponent can't control, thus the flow of Nature chakra could break or even prevent any genjutsu in theory.
Sage mode by itself enhances what the user already has, and fusion mode adds combination jutsu. Remember when Pa toad said Naruto mastered Sage techniques and Frog-fu (taijutsu I assume). Jutsu=techniques, so he learned some that don't depend on fusion. It's a hard question actually. Kudos.