This is now an old question, and I'm surprised no-one has suggested this already:
If you can log in as root (if it's your instance, so you can make it so), then you can mount a part of the remote file system in a variety of ways, and you can then use your preferred graphical editor on your local system.
sshfs is one such option:
sshfs root@host:[dir] mountpoint [options]
Be careful with this though. You can make very big mistakes easily. I wouldn't use a graphical file manager with this, as it's to easy to make a mistaken mouse move and move a whole directory or something like that. I'd also hesitate to mount a directory which is likely to have active changes going on remotely.
In a similar vein, and with similar caveats about graphical file managers, many linux file managers (e.g. nemo, which I use) can open a remote directory by giving it a path like sftp://[email protected]/dir/ect/ory, which performs a file mount, allowing local apps to edit the remote files.
Some file editors (e.g. the Gnome text editor) will allow you to paste an URL like sftp://[email protected]/dir/ect/ory into the file open dialog to access files in your remote folder as root.
I use a variety of approaches. I commonly prefer to use something like rsync or git to periodically sync files, as it gives a lot of added safety, but mounting a directory has advantages. It often gives me a really tight testing cycle for seeing the effects of changes, and it allows me to use command line editing techniques to do things like search and replace across whole directory structures. I can do those things remotely also, but for example I can mount servers from multiple hosts onto my local system and do operations between them.
netrwmodule meets this need. Use the gvim version, and there you have your graphical editor.