It's not that French guys wanted to build a spaceport in the middle of nowhere in Guiana, just it's easier to reach geostationary orbit from the equator. Also if things go wrong you really need a large uninhabited place to the east.
For the goals put forth in the document (higher inclination orbits), I think it's not much of an impediment to launch that far from the equator. Plus I think even if you're going to GEO the penalty for launching further north isn't that bad in terms of delta-v. It's probably less than what Israel has to deal with (they only launch into retrograde orbits)