Oops! The disabled button is a UI issue, it was intended not to allow changing the boot volume from basic to logical. You could eventually use SDK though it is not trivial.
As for grub-install, you are looking in the right place. Well, the binary can be renamed and added a shell script with its name which does the job of calling it and translating "-v". Not trivial either but easier than starting to use SDK
There doesn't seem to be an easy workaround but after all Ubuntu 14.04 is not supported. Neither is BtrFS by the way. If you manage to run the conversion, it will be converted to ext3.