Darcy-Rose/Darcy-Mae - I like both a lot. :)
Ruby-Leigh - Very pretty. Ruby is also on my list.
Felicity-Rose - I have seen Felicity used recently and it was very refreshing.
Maisie-Isabelle - I'm not sure if I like this one hyphenated because the 's' sounds run together a little "Maisie-Isabelle". Otherwise, it's a pretty name.
The only one I don't really care for is Atlanta-Skye. It's just too wordy. Like you are talking about the sky in Atlanta, Georgia. I'm not sure if you are in the US or not but this is the first thing I thought about.
ETA: To answer your other question, I like Kelsey (prefer this spelling) more than Chelsea.
Other names that might fit with Phoebe and Teagan:
Felicity-Rose- Although I don't see this going as well with Phoebe and Teagan.
Others: Stella, Cyan, Cora, Coraline, Coralie, Kylie, Kiana, Quinn, Reagan, Kennedy, Kenzie, Kelsey, Cambria, Eden, Embry, Harper, Hadley, Marley, Miley, Imogen, Isla, Ivy, Jordana, Nova, Paisley, Peyton, Rosalie, Sadie, Shelby, Tamsin, Tahnee, Winter, Summer, Autumn, Juniper, Willow, Zoe