Answer: No, it is not possible to replace the integrated 7-speed cassette on LG1 hubs with a different freehub body or cassette.
The integrated 7-speed cassette on LG1, LG1+ and LG1r rear hubs are narrower than a standard 11 or 12 speed freehub body. We made the cassette narrower so we could move the drive-side hub flange outboard to build a stiffer, stronger wheel. As a result, it is not possible to install a standard freehub body on these hubs, as they are too wide to fit!
We offer replacement integrated cassettes as a service part so you can continue to enjoy your LG1 hub for years to come: FWS10-104 LG1 7 speed integrated cassette