After some struggling I've managed to add exFat support to my synology. I had to compile some stuff and I did it natively using optware gcc, automake, etc.. ExFat disks aren't hotplugged, but I've put up a minimalistic php page that launches bash scripts to mount/unmount drives without having to login via ssh. I'm not a bash expert and my scripts aren't perfect, but if there's someone interested in this, I can put up a how-to