Cockrum came up with the team of space pirates known as the Starjammers in 1972. He submitted the idea to Marvel Spotlight and Marvel Premiere, the tryout/anthology books, but was told they were booked for two years in advance. So he went to Chris Claremont and convinced him to put the Starjammers into X-Men... with some changes.
Rather than Corsair, the leader of the team would have been a guy called Bloodstar:
If you remember Dave's other creations, the Strangers, you'll recognize Phaedra as being a reworking of the character Belladonna from that pitch, who would have been a vampire lady and the Wolverine character's sister:
In 1994, Cockrum partnered with Action Hobbies to release a model kit of Phaedra, which revealed some of the original intended 1972 Starjammers story:
Phaedra is a warrior princess of the planetary republic of Shandilarr; she is also a Genjaak Sorceress and member of the Bright Council of Llangobar.
Driven from her homeworld when it was destroyed by the Dark Empire, Pahaedra, with her chief warlord Bloodstar, formed a resistance group to combat the Dark Empire. The called themselves The Starjammers...
For his part, Claremont tried to convince Cockrum not to use the Starjammers in the book - not because he didn't think they were good characters, but because if they appeared in X-Men, then they'd be X-Men characters: if they appeared somewhere else first, Cockrum would still have claim to them, and could possibly get royalties for it. He even offered to drop their scenes from Uncanny #107, and write around the absence. But Dave was excited about the team, so into the book they went, which is why today we have Corsair instead of Bloodstar.