We don't remove LSM in grsecurity. Users are free to use any LSM they want. It's clear there's some sort of a need for either stackable LSMs or some sort of a way to get *optional* security features merged without having to fight with anti-security kernel developers for months. There's already a number of security features whose options are spread out all over the kernel, things that aren't a complete coherent model but rather serve a particular security purpose: config_debug_rodata, stack protector, builtin_object_size checks in copy_from_user, mmap_min_addr, etc.
As for building the LSM people want, I would urge others to research the history of LSM, the commercial interests of the time, how those interests became public, how Linus nearly removed LSM, why it was later almost removed again to force people into using SELinux, etc. You're likely not aware there was a competing framework that got tossed in favor of LSM due to some nasty behind-the-scenes politics. I'll try to dig up some emails I have on the topic.