The videos I've seen show the full roof being removed (but maybe different models Thor/Hercules are installed differently):
View attachment 7794268
but then the original roof/courtesy lights are installed in a new console:
View attachment 7794269
So, I'm guessing, the full Ineos Grenadier top panel could either be replicated in the Alucab roof console, or it maybe could be incorporated in. The fact that the roof light wiring needs extending may need more of the same - or better still some form of plug in extension harness?