I dont do intarsia on my patterning machines. I did it on my Bond way back when it was all I had. Other than taking care to cross the yarns between colors, it was pretty simple. But the Bond had no tensioning mast & all the yarns went through the machine in an almost normal manner when laid in the open needles for intarsia. I think doing it on a machine would befaster than hand knitting. But you have to watch every row like a hawk. (Being sure yarns are crosses consistently.
As for casting on in 2 colors, I’d use a waste yarn , ravel cord, then cast on each block separately, crossing the yarns as for intarsian on tahat row. But from what I can see you rib the bottom anyway. In which case you could start your intarsia immediately after it is done. Or if you dont have a ribber, you could hand knit the rib & hang it, then proceed with no need of additional cast on. Are you trying to bring the patern down into the rib? I could be wrong but it looks like there is a narrow rib (or maybe hem) at the bottom of that sweater.
I have a globe pattern in a back issue of Vogue (circa 1990s) by Patricia somebody. It has a great big textured shawl collar & I always admired it. But never got around to making it. She was quite a popular designer back then. I think her continents were larger relative to the background. Not sure. But this one seems to show more background than hers did.
Both versions are stunners, imo.