If I had the cash to burn on a 120L SUP with a foil track and a Naish Thrust Foil I would totally give it a go for foiling with my 12m kite.
reasons:
- I like the adventure of going places when foiling, often 5 km downwind then 10 km back upwind. Having a 120L SUP to knee paddle back on if the wind dies would be nicer than swimming to shore and walking.
- Where I live we aren't allowed to kite at the good beach in the summer but we can windsurf and sup. I would have to knee paddle out and then drift launch my kite but at least I could use the nice beach near my house.
The way I figure it is if windsurfing in 8 knots on a 120L SUP is fun then kitesurfing that same board would be more fun.
I'm not sure that either actually is fun though, and not willing to drop over $2k to find out.