Naruto need this because Kurama is stronger than him he can't just access all the chakra or Kurama might take over him... So6p made the Juubi his bitch, he didn't need to ask for his chakra, he could just take it, he had already proven he was superior to it and the Juubi knew he would be spanked big time if he ever tried to take over
I am sorry but I kind of agree with the OP. Yes Rikudo did become the first Jinchuriki but I too believe that he was an imperfect Jinchuriki not in the sense that he didn't have control but in the sense that the Juubi most likely didn't give him full control of his power.
Just like how Naruto could use Kurama's power sometimes when he wanted but most of the times before Mastering it he had to ask. Also even then the Hachibi told Naruto that his relationship with Kurama would be a amajor factor in how much power he got from Kurama. You have to remember that Kurama was put in the same SEAL that the Juubi was put in and even then Naruto didn't have all of his power. So just think about if Rikudo seperated the Juubi's chakra from him?? He would have a super duper mass amount of chakra without ever having to ask for any for his entire lifetime but it wouldn't be everything because the Bijuu still has to cooperate with you in order to gain all of his power like how Kurama did for Naruto. Plus we knew that he didn't have a great relationship with the Juubi casue he admitted it himself and foretold that someone would come along and do what he could not do in his lifetime.
So to go over everything:
1. I don't doubt Rikudo's power but he himself admitted to not having a good relationship with the Juubi. I think yes like the OP said the names mean a lot and I don't think that Rikudo knew the Juubi's name because like he said they have a good relationship so their was no trust. I am not going to go into all of that because all of the Bijuus explained the reason behind it so I am sure that same reason was probably imprinted on the Juubi. I mean Rikudo couldn't have been the first to come up against the Juubi unless he created him himself.
2. Rikudo and Naruto both had the exact same seals on their Bijuu so there is no other thing that Rikudo could have done different than Naruto to the Juubi other than take/master his chakra.
3. Just like Naruto the chakra would run out but in the sense for the Juubi who had unlimited chakra it would have been a long long long time for him to ever run out of chakra. Then you have to think about it, there was no one to oppose him especially since he was creating ninjutsus that no other person has seen before so it wouldn't really be any reason for him to go all out like Naruto is doing right now. He would be able to use some of the simplest forms of ninjutsu to subdue his enemies but even then he had taught everyone else how to use ninjutsu so even if they didn't fight him they soon wanted to fight each other. He went around the world and taught many nations including his two powerful sons. Rikudo himself didn't start the hatred but gave everyone the fire to become a nuclear deterrent by first teaching them ninjutsu and then releasing nine powerful Bijuus to take over causing even more damage. He knew that with all that he had taught them that someone would come along and SEAL the juubi which is the reason why he split the Juubi in the first place. Why? Because if any one nation would have taken over the Juubi they would have unlimited chakra to take over Nations. With everything he already taught them their power would have been enhanced 10000x over.
4. Even being a imperfect Jinchuriki Rikudo would have still been powerful enough to take over Nations because of the fact that he gained the Rinnegan from the Juubi. Just that alone and damn near infinite amount of chakra made him THE major threat. With the Rinnegan he had control over every elemental release(including every kekkei genkai in existence), control over yin and yang release, six paths(which we know first hand to be super powerful so adding in powerful chakra OMG), sense chakra, and seeing chakra. So it is no wonder he could use Creation of All Things because he had a large chakra pool to pull from especially being able to fully manipulate Yin and Yang Rlease.
5. Rikudo himself foretold another that would come along and reunite them all again. This person was to bring them together into the Juubi and have a better relationship with them/Juubi than he ever could. So if Naruto gains the trust of the Juubi and gains the trust from it so that it would give him total control over all of his chakra then yes I could say that Naruto would become more powerful than Rikudo himself.
6. I want to quote the (OP) Supreme N8:
"Its like when the nine tails was sealed in naruto, He was evil and Naruto had to be cautious not to release him and not to use to much of his power due to his evil nature. Now that kurama is good he can completely access his power & release him and work with him on the battlefield."
The only thing that don't sit with me is the fact that Naruto had to be cautious because he didn't put that powerful SEAL on him then. Before he had to ask for Kurama's power which I believe was the same situation with Rikudo Sennin. Which at the time means that even if he did lock him down with a powerful SEAL he still wouldn't gain all of the Juubi's chakra unless the Juubi gave it to him.
There is one thing that the OP was wrong about and that was the names of the 9 Bijuus. Dude he created them through Creation of All Things and named them afterwards. Only Rikduo himself didn't even know the name of the Juubi.
