In May 2013, CAF announced the qualifying format for the 2015 Africa Cup of Nations (hosted by Morocco).
With all the 2014 FIFA match dates used for the 2015 qualifiers, it means the preliminaries for the 2017 ACN and 2018 World Cup will only start in 2015. The preliminary draw for the 2018 FIFA World Cup will take place on 24 or 25 July 2015.
CAF can't use the 2010 WCQ system because back then the World Cup and the Nations Cup where held in the same year.
I think the best option would be to take a page out of AFC's book. It's in CAF's best interest to send its best teams to the World Cup and also to give them matches against quality opposition during the final stages of the qualifying. That's because they obviously want more spots at the World Cup (don't they all?) and the confederation weightings used in the FIFA ranking calculations are based on World Cup performance of each confederation's teams. The playoff for the 2014 World Cup could have Egypt meeting Côte d'Ivoire and I think CAF would rather have both teams making it to Brazil.
1. First stage
Home and away matches to reduce the number of teams to 36. To be played in March and June 2015.
2. Group stage - draw taking place in July 2015.
Six group of six teams, top two advancing to the next stage. 10 match dates are needed. The best 15 teams qualify for the 2017 Africa Cup of Nations.
3. Group stage
Two group of six teams. Top two advance to the 2018 World Cup, the third-placed teams play-off for the final spot. 10 match dates are needed for the group stage and another 2 for the play-off.
22 match dates are needed for the two group stages and there are 26 available (6 in 2015 after the draw, 10 in 2016 and 10 in 2017).
So, looking at the July ranking, this is how things would look like:
1. First stage
Pot 1: Uganda, Gabon, Sierra Leone, Congo DR, Central African Republic, Congo, Angola, Ethiopia, Mozambique, Liberia, Niger, Malawi, Zimbabwe, Benin, Botswana, Burundi, Tanzania, Kenya
Pot 2: Namibia, Rwanda, Sudan, Chad, Lesotho, Gambia, Sao Tome e Principe, Mauritania, Swaziland, Guinea-Bissau, Mauritius, Madagascar, Comoros, Eritrea, South Sudan, Seychelles, Somalia, Djibouti
2. First group stage
Assuming the seeded teams advance for the first stage, these would be the pots:
Pot 1: Côte d'Ivoire, Ghana, Mali, Algeria, Nigeria, Burkina Faso
Pot 2: Tunisia, Cape Verde Islands, South Africa, Zambia, Guinea, Egypt
Pot 3: Equatorial Guinea, Libya, Cameroon, Togo, Senegal, Morocco
Pot 4: Uganda, Gabon, Sierra Leone, Congo DR, Central African Republic, Congo
Pot 5: Angola, Ethiopia, Mozambique, Liberia, Niger, Malawi
Pot 6: Zimbabwe, Benin, Botswana, Burundi, Tanzania, Kenya
3. Second group stage
Assuming the teams with the better Elo rating (yes, I'm cheating a bit :) ) advance from the previous group stage, these would be the pots.
Pot 1: Côte d'Ivoire, Ghana
Pot 2: Mali, Algeria
Pot 3: Nigeria, Burkina Faso
Pot 4: Tunisia, South Africa
Pot 5: Egypt, Libya
Pot 6: Cameroon, Senegal