Would not have made a difference. They were out numbered & out gunned. Sitting Bull had all the cards.
It is a certain thing that Benteen advised Custer that it would be best to keep the whole outfit together considering the size of the trail they were on and was rebuffed. I have been there several times and I believe had Custer followed Benteen's advice and attacked the village with all 12 companies including the ammunition mules, on the flat ground that Reno made to initial attack on there is no way the Indians could have overcome the superior Springfield rifles. If you notice there were 7 companies on worse ground that held off the Indians for the next 36 hours until General Terry's approach caused the Indians to head for the hills.
As to why Custer did not get rid of Benteen, I suspect General Phil Sheridan wanted Benteen in the 7th Cavalry as a good influence on Custer. I think it notable that Sheridan found no fault with Benteen, Reno, or Terry. And President Grant blamed the whole fiasco on Custer.
