I'd rather see the inverse: a Linux kernel with BSD userland, filesystem, and ports. But that doesn't fit with Debian's strengths as a package repository. Installing packages to different paths on different systems is not really feasible. Using ports means Debian has nothing to contribute, since it completely replaces the Debian package system.
On the other hand, swapping out just the kernel is a natural fit for their system. All they have is a hammer, so they found a nail. Unfortunately it doesn't result in a very appealing OS, since the kernel is not really the selling point of BSD. It works, but it's nothing special. The magic is in the BSD userland.
"The doomsday scenario of choosing between (a) and (b) becomes less likely if we make it clear how bad it would be. We need to provide appropriate backpressure to encourage upstream decisions that support the continued freedom of our users."
In other words, Jackson is willing to drop GNOME from Debian to pressure GNOME developers into not making dependencies on systemd.
He wants the doomsday scenario of choosing between (a) and (b) NOT to occur. By making it clear how bad it would be.
So yes, he wants to make it clear how bad it would be, but he's also the one who's pushing for making it bad. It's not like he's just warning us that someone else will make Debian choose between those two things, he's trying to make Debian choose between them.