I would trade gamzee post rampage for eridan surviving (provided we also stop him from destroying the matriorb)
It didnt make sense how he blasted the matriorb after all that talk and he sure as shit could have gotten away with killing sollux and feferi if he hadnt shot the matriorb. If Gamzee can get away with a dumb rampage, I dont see why Eridan cant.
How I would do it is have Eridan take Kanaya hostage, have her talk him down by addressing his loneliness using her own solitary life in the alternian sun to sympaphize, then have him save karkat when gamzee doesnt calm down. Have him save Equius and Nepeta, kill one of those two off, the other vouches for Eridan so Karkat doesnt go apeshit and kill him>note: Karkat still goes apeshit