Courf would be the guy who ropes all of their friends into helping him propose to Combeferre, think whole musical number to "their song" which Combeferre blushes through the whole time because he cant believe Courf has really done this except he can because its Courf. So Courf gets to the end of his performance, everyone is huffing with exertion cause it was really that intense and Combeferre is like "I think I need a little more convincing you wanna marry me" so Courf gets down on one knee :D
He's down on one knee in front of Combeferre, reaching into his pockets for the ring, when he turns over to Grantaire, Joly and Bossuet, all of whom are holding camcorders facing them from different directions, and says to Grantaire, "Make sure you pan in on his face, close enough that we can see it if he tears up."
Grantaire salutes him. "Yessir."
Courfeyrac turns back to Combeferre, who is grinning at him, because shit, Courfeyrac is the most ridiculous person, and Combeferre is so in love with him.
"I'm going to have to warn you first," Courfeyrac says with a small smile, taking Combeferre's hand in his. "This proposal is six minutes long. I go through all our relationship milestones in my speech."
"You dork," Combeferre says, grinning wider. "Go on with it, then."
Courfeyrac takes a deep breath, and does.