If you really want to, you can create a helper partition on the internal drive that has the kernel and /extra folder (for the extension cache). You'll need to edit the boot plist so that the kernel knows to boot off of the sdhc card (easiest way is with a root=uuid)
The steps to do this are basically
1) Install the os to the sd card as usual (making sure netbook install is run on it)
2) Create a helper partition on the internal drive (or a usb drive) and install chameleon to it (you can use NBI to do that)
3) Copy the /Extra folder on the sd card to the internal helper partition
and finaly, setup the boot plist on the internal drive to point to the sd card.
This does take a few extra steps verses the normal install (say 5 to 10), but it's doable. The sd driver fro mac os x isn't very good, so you will have performance issues as well as a higher chance for data loss.
The same thing goes for booting linux from the sd card. You'll need a helper (boot) partition on the internal drive with the kernel and driver (and any ramdisks you might use).