Uruguay, Paraguay and Argentina are also hosting games, partly to make a token recognition of the 100th anniversary, but mainly to provide a route for Saudi Arabia in 2030 (eliminate three continents from the rotation).
Instead of the single game each currently planned, they could play a whole group in each of those countries. Then they'd have 13 groups for Morocco, Portugal and Spain. That should be easy to manage. Morocco are building quite a few stadia.
This might be the path planned. Distribute the group games among cohosts and play the knockout games in a primary host (pretty much like this world cup). The Euros did a similar things with cities recently. I assume this would be necessary for a 64 game world cup in Saudi Arabia. I'm not sure the Saudis can manage 48 teams, so the expansion would be a convenient excuse for spreading it around, rather than admitting the chosen host is inadequate.