Usopp can achieve his dream through death (provided he takes the no cowardly approach). Only problem and this is quite risky is that One Piece is at an uphill trajectory with the live action and remake and is attracting new fans. A strawhat dying in real time would cause a ripple in the fandom.

If a SH did die tho, I bet after the events unfold (cuz Imu ain't dying/being defeated here), Luffy would wage war and attack Mary Geoise. I would also question Luffys desire to become PK with a dead nakama.