This has nothing to do with a MMU. You cannot run compressed code directly anyhow, so it does not make sense to remap anything to anywhere. As compressed code requires decompression first, and the ROM area would be populated (otherwise compression would not make sense), you need to decompress to RAM, and as you decompress to RAM, you need to relocate as you do not know where the target RAM will be.
This is neither related to SKick, as - again - SKick maps the ROM to RAM, though with relocation information - but mapping a compressed image to some place makes neither sense.
One way or another, this is not a good option. It requires more RAM, not just the decompressor, and as most users use hard disks anyhow, it is much simpler to load the modules missing in ROM from harddisk instead. It also makes the kickstart more flexible.
The kickstart comes with sufficient components to give you access to the system, and - starting with 3.2 - also with sufficient functionality to update many modules from harddisk should the disk contain newer components. There is really no need to spoil RAM for compression that is not needed.