The best replacement for kernel is rom.

The best alternatives to kernel are rated as following:
★★★★★  rom
★★★★★  os
★★★★  user mode
★★★★  colonel
★★★★  shell
★★★  user space
★★★  user
★★  firmware
★★  null space
★★  microkernel
★★  kernal
★★  user threads
★★  bios
★  rom first
★  windows kernel
★  linux kernel
★  operating system
★  nut
★  palm oil
★  white kernel coconut oil
★  small memory dump
  faux123
  whole kernel coconut oil
  franco
  kernel linux

Your alternative for kernel is not listed? Suggest!
Speaking about kernel, one probably shouldn't forget about initramfs.

Other search terms related to kernel and their ratings are:
★★★★★ initramfs
★★★★ initrd
★★★ pae
★★ yum
You have in mind a companion for kernel and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of kernel in all years. Click on graph for more.
kernel
rom
os