One pitfall of this is that the decompressed contents of your initramfs must fit within half of your physical RAM since Linux decompresses it into a tmpfs.
Or if you set rootfstype=ramfs, then you can take up to all of physical RAM, but ramfs isn't swappable.
Or if you set rootfstype=ramfs, then you can take up to all of physical RAM, but ramfs isn't swappable.