This is exactly my point. Why would LH need SN in BRU when they can do everything from FRA?The answer is simple. BRU can't provide the connections FRA can. How does an oil worker go from Houston via Brussels to Point-a-Noire??? Oil routes will always be offered from FRA (or ZRH) first as they can offer the oil workers the necessary connections to the world. BRU is ideal for AFI flights which don't need too many connections from outside Europe, not when you need feed from the oil cities around the world.
My next point is that BRU is alot better positioned to attack the French market to Africa, a significant one. So why would LH fly from FRA when they can focus everything in BRU?
Conclusion: It can be one way or the other but you can not make everyone happy by using 3 hubs for Africa and pretend to serve everyone with them. AF-KL has been doing this with AMS-CDG and it is clearly not working or otherwise AF-KL would not have lost 1,5 billion.
It is better to focus on some markets, forget the 20 oil workers who come from Houston every year and use Diabolo/Thalys to serve the thousands of French oil workers living in Northern and Southern France from BRU, together with pax for BZV.
Or put simply, using three European hubs for Africa is going to be a huge mess. LX, SN and LH are already competing on some routes while smiling to eachother. Pathetic it is. At this rate they will hurt themselves more than they will hurt AF.