I like this idea and it would also be interesting to have better relationships between countries with the same language. I know it is probably hard but groups like:
Portugal, Brasil, Cabo Verde, Sao Tome, Angola, Moçambique (IRL TAP Portugal favors these countries)
Spain with Latin America Except Brasil. (irl Iberia)
France, Senegal, Cote Ivoire, Mali (irl Air France)
UK, Nigeria, Kenya
Regarding demand, I think I've read that there is no table, so no chance to influence demand between same language countries.