About lapis, i don't think she's evil, and i think what happened to her was different of what she thinks, i have good expectations for her because liking steve (and locking herself in the dephts of the ocean for him) is a good start for a character change, still, she would be the only one that could join the crew (when learning more about her past and what really happened), but it's very unlikely since she's so strong. (Most of the plot is in earth so don't say she's weak when away from water)
About Peridot, at first i don't really liked her but after jailbreak and knowing she's lost on earth, i can't stop think about the many possibilities and what can happen now, Peridot is not evil, and is not a warrior!!! She's a engineer doing her job, she's been "brainwashed" in homeworld to believe that gems are superior and the rest is just animals, now she came for a "easy job", found rebel gems with ancient battle styles (Summoning weapons? Fusion?) and maybe now is going to discover many secrets that the diamond authority was hiding (most likely). What i really like on Peridot is her personality, deal with this many new things while still being all pride and superiority is something i'm curious to see(Not that frail and cute personality fans has been dreaming about... not that i hate it.. it's cute, but it's also so not-peridot). She remembers me a lot of Vegeta (But not powerful as him tought..) and i think she had a good chance to join the crew but after at least one season and many many maaany situations.. or she will just appear in a new robot and be punched to space......
Now Jasper, i like her, she's a villain, she do things villains do, she hit a child, well fine she's evil what do you expect? She's a war veteran and has her reasons to be like that, and i'm curious to see that, being SU it's probaly a reason full of feels regarding Rose and her rebelion. She's too loyal to Homeworld and even if Yellow Diamond just betray her for some reason, she will still not join the crew, Garnet (or at least Ruby) would never forgive her..