I visited Gabon last year and explored some extremely remote rivers, and I did it with guides (not my preferred method, but unfortunately necessary in many parts of Africa). I paddled the Ntem in northern Gabon, and also a couple of tributaries of the Ivindo. I believe, based on these experiences, that there is definitely scope for packraft exploration of rivers in Gabon, provided (a) you don't go solo (for security reasons), and (b) you don't stray too close to borders (Cameroon, Equitorial Guinea, the Congo, etc). I'd love to do a trip where I brought along a local guide (so you can speak to people you might meet along the river,so as to allay suspicions about what you're doing, and translate for you). The guide could be in a dugout, or you could provide a second packraft for him.
Just a few thoughts. It's a wild and beautiful country, and safer than most in Africa. Expensive, though. And keep in mind, wildlife is hard to spot on these rivers, especially ones that are easily accessible to hunters (which is most of them).
The Gabon trip I did appears as a twenty minute Bonus Feature on my DVD 'Packrafting the Kimberley', which just came out (August 2011). It's available (I ship anywhere in the world) from my website at www.remoteriverman.com