I wouldn't do it myself. But ajschot seems to be reporting good experience, at least with respect to CrashPlan.
yes it works well, but if you need something like jails then NOT go to corral also it will be hard to switch later on back. But for me Corral has everything but if you start then go to 9.10.2 and use iohyve to install debian and install in Debian CrashPlan... there are a lot of manuals for this....
But if you want easy way (Corral is easier still!) I red in the official announcement that is had no iSCSI, strange... because it does! I have it running... but ok... for iXsystems it is not the best because they canned it, so no update's and no bugs are going to be solved. (but again it works for ME and I like it more then 9.10 it is not that you have to do it)
If you want the most stable way (in some oppinions) install FreeNAS 9.10, install Debian or Ubuntu in iohyve (you can do this via SSH, i think it is in this thread page 1 or 2??) and then in Debian or whatever linux you want, install CrashPlan for Linux and be sure it all starts automatically when FN9 starts and be sure you use and setup NFS share in FreeNAS and in you Linux VM.
I had it in 9.10 but it was clunky buggy way but it will do something.... that is one of the reasons why i am still on Corral.
Also you can install ESXi (FreeNAS geeks does not like this way too) and make a FreeNAS VM and a Linux/Windows VM and install CrashPLan in Linux/Windows and use a NFS or Samba share to connect your network in the VM.
or do it the FreeNAS way and wait till they have dockers back again