I see your point with some stuff, but I slightly disagree with some others.I never said that Naruto and Sasuke don't have Sage Chakra. I simply stated that if the chakra is gone from from their bodies, then, at least Sasuke wouldn't lose Rinnegan. The mutation has already happened. Just like, for example, Kakashi's Sharingan mutated because of Obito. A sharingan cannot mutate without the release of a special Uchiha chakra within the head. But the mutation had happened, and the eye had already changed. It was not going to revert back just because Kakashi didn't release Uchiha chakra into his brain.
Second we have Nagato's example. Madara was the one who experience the mutation in his eyes. But the eyes had already mutated. Even when they were parted from the original chakra source - whether it was inside his brain or body - the eyes still remained Rinnegan and Nagato kept using them. This is the best way I can explain it.
With Sasuke, I agree. Even with Hogoromo's chakra, he shouldn't be able to shift dimensions. As 1) it's half the chakra and 2) the technique is too taxing even for Kaguya whose chakra far exceeds Hogoromo's full reserves. But, he is able to. Why? Because 1) his Chakra Control is at the Sage's level, and we know from part one that the more the CC, the less chakra is used and viceversa. 2) His chakra is extremely powerful and he can manage far more with less. We have known this from the start. 3) He already had a similar technique and got better.
These three factors make up for the large chakra. That is the only logical explanation.
That is slightly wrong. Naruto, for one, cannot use two Sage Modes at the same time, so it certainly isn't a combo of BSM and Sage of the Six Paths mode, which is RSM. When he kicked the orb, he was using RSM. He was given Senjutsu chakra from the sage, which results in "Sage of the Six Path Mode". This, combined with the chunks of chakra from all Bijuus results in that black and yellow cloak and TSBs. It isn't an RSM cloak. If you recall, Obito immediately gained a TSB when he pulled out Senjutsu chakra and Bijuu chakra from Madara's body. This Senjutsu also allowed Kakashi to use that ill-fated PS.
I don't believe both of them have lost Sage's Chakra. It seems less possible for Sasuke, to be honest. The meeting place has nothing to do with Sage Chakra, it's just Ninshuu; something Naruto did well before he even combined his Chakra with his Frog Sage Mode. My two cents.
1. You said that the meeting place thing had to do with ninshuu, but that actually had nothing to do with ninshuu. Hagoromo specifically stated that Naruto would be the meeting place because Naruto had all the bijuus' chakara. Remember that all of the bijuus even showed up inside of Naruto's subconscious when Naruto was talking to Hagoromo (when Hagoromo asked Naruto what his plans were after the war). Those bijuus were able to show up because their chakara was inside Naruto. Furthermore, bijuus are able to telepathically communicate with other chakara manifestations of themselves (as evidenced by yang Kurama who was in Naruto asking yin Kurama who was inside Minato at the time for some chakara during the battle against Obito even though Naruto and Minato were a good distance away from each other). That is how Naruto is supposed to be the meeting place. All of the bijuus, no matter where they are in the world, should be able to communicate/connect with their own chakara manifestation that is inside Naruto, and in turn that chakara manifestation inside Naruto could communicate with the other bijuus' chakara manifestations inside Naruto. You are right however, in saying that this meeting has nothing to do with rikudou chakara. It just has to do with bijuu chakara.
2. I disagree that the rikudou chakara is gone from Naruto's body, as the mode Naruto is using in Gaiden does seem to be RSM. Now remember the fact that as you said, RSM is actually the form that Naruto donned when he kicked Madara's truth seeking ball (which was near identical to his base form save for the BSM looking eyes). The cloak and the truth seeking balls came from RSM+bijuu chakaras. Now notice that in RSM (the one that looks like base Naruto), Naruto lacks the toad sage mode pigmentation around the eyes. The same statement holds true even when Naruto does apply the bijuu chakaras and gains the cloak and truth seeking balls. Well if you look at Gaiden Naruto's mode, notice that he has the BSM/RSM eyes, yet he lacks the toad sage mode pigmentation around his eyes. This implies that it is RSM. His cloak doesn't have truth seeking balls as well as the magatama and rinnegan symbol on his back because he is using RSM and applying only Kurama's chakara (not all 9 bijuus).
At the end of the day, whether or not Naruto still has the version of RSM we all came to know back in the war depends upon whether or not he has the other bijuus' chakaras.