You should look sshfs for the core2-32 architecture, then download the repo with wget. Uncompress the file with tar xvf <filename> and follow the steps on this guide http://alextgalileo.altervista.org/edison-package-repo-configuration-instructions.html . Then, run the command opkg install packagegroup-core-buildessential and finally install the package. Let me know if this works.
I guess you want it the other way round: installing sshfs on the history and mount the target into your host fs?
I was looking for a way to keep things backed up nicely in a host computer. For example, I would like to keep all code on a Mac OSX folder (where I have Dropbox backing it up in addition to daily backups using Time Machine). I could then develop right there on the Mac - and just switch over to a terminal window logged on to the Edison to compile/test the code.
Is this reasonable and/or a good workflow ?
a, ok - you could do so. I just did a quick test Yocto building sshfs-fuse for Galileo taking the openembedded sshfs-fuse recipe. Works fine and should work similarly for Edison.
(If you want to compile directly have a look at the recipe and directly build it on the target).
That said: if you are on C/C++ you might be interested to Eclipse IDE from Intel(R) IoT developer kit (https://software.intel.com/en-us/iot/getting-started). That way you can host, develop and build projects on the host using the cross compiler as well as remote debug.