Well, it is true that having 1 boardbag is quite usefull. Until now, that's what I did: use Air France or any other company that let you bring one GOLF bag extra for free, and load it good, even when I did not bring a board... Hell, I even put a foldable baby cot in there once! If it does not weight more than 20kgs, they just send it through...
And since I leave from a country where Kiteboarding is a marginal sport, they do not know of the ruse at checking counter... The problem is when you get back: flying back from Tarifa, through the airport of Malaga, where they sure do see their share of boardbag getting checked, I did not dare risk it, when they would ask 150€ for the boardbag on the trip back alone... I changed airline, it came out cheaper this way...
So having a splitboard can save quite some money, and I did not verify it, but I believe that I can keep the weight of the "kite luggage" with board, harness, 2 kites, pump, wetsuit etc... under 20 kgs, which leaves 3 kgs for clothes.... that is not much, so I'll keep in mind the trick of using a kitebag as cabin luggage....
To sum up: if you are pretty sure you can get away with a "golf" bag, then yes, use one, but it is nice to have the option of the splitboard in case it does not look good on the way back...