And you have no idea how large Hashirama's would have been if given Naruto's powerup. He would be a pseudo Juubi Jinchuriki, and his base Mokuton was already capable of easily changing a battlefield, now add all the Biju chakra
The only thing that would change is that he will get truth seeking orbs. That's really it.
When naruto blossomed rsm, his kyuubi chakra cloak didn't get any bigger and nor did his bijuu transformation.
So his kekkai genkai will not be affected in a positively or negatively by a different kekkai genkai.
There is no pseudo juubi jinchuuriki, the juubi is the divine tree itself, it's not going to surpass that level either.
Psuedo JJ would be having the pieces of the Shinju with the exception of the Mazo (which is what Naruto had)
And Naruto's Jutsu got a huge buff when he got RSM, coming from an Edo Madara absorbing his RS, to completely overpowering a JJ Madara with a LRS