Can't believe some people honestly believe there'd be no problem at all.
Well... Let me tell you what happens. Instead of a show revolving around fighting akatsuki and tobi, it'll be a show about fighting Kages, Anbu assassins, spies, etc. Basically, NV would be like always with one village fighting another until a 4th shinobi war broke out.
Naruto would still need/have sage mode.
Sasuke would need to get MS (most likely itachi would still train him to get it without itachi having to torture him).
orochimaru would still be evil and form the sound village
Minato would have to be dead some how because obito isn't becoming hokage while minato is fit to fight. MS obito was no where near as big a threat as minato.
In the end, Minato, kushina, hiruzen, jiraiya would all most likely die one way or another due to village disputes and fighting. The final villain would probably be orochimaru and his sound village as he already assassinated kazekage and hokage for his own personal reasons. Orochimaru's plans, as far as we can tell, have nothing to do with obito or madara so he'd still carry out his evil plot. Orochimaru with his immortality, DSM, an uchiha body with sharingan (he'd get these 2 to be a good final villain). in fact, essentially an orochimaru with DSM kabuto's powers, except that instead of having to use tayuya jutsu to call out the sound 4, oro would have integrated doton jutsu, and kimi's bone KKG into his arsenal through body replacement.
TL;DR; Oro would be the final villain. Instead of some crap about a juubi and huge explosions, it'd be a hax village of crazy village of cursed mark warriors, a DSM-sharingan user and an army of Edo tensei's (madara, hashirama, tobirama, etc. but with less hax). Would probably make for a better climax
