I was looking into this myself and I believe they have Directed Electronics has Xpresskits module with firmware for 2013 GS350 for Remote Start. This may actually work since the vehicles are pretty close to same generation in electronics. I am slowly going over all the plugs from the diagram and seeing if they match up to the 2014 ISx50 and if they look like it is I will be attempting install using this current firmware.
I am an Professional Installer so this is why I am willing to attempt this.
If there any another installers out there that look into this as well lets compare notes