Note: This is some idea feedback  that was inspired by reading the journal of the game. I currently never played the beta yet.

In my point of view, there should be no dependencies to special ressources. I hate it in CIV IV when there is half of the unit types I cannot build because I don't have horses. Which mean that special ressources should give bonus.

On the other hand you want players to be somewhat dependant on these ressources so that they are worth trading and make it interesting to attack key cities which holds unique ressource to that player in order to destabilise him.

My suggestion is to make to bonus received by the player incremental. For each ressource you have you gain let say 2 points, but for each type of ressource you get, you increase the amount of points each ressource gives you. TYpe multiplication would be applied to the same type of bonus. For example, special ressource that boost production will not multiply special ressource that boost food production.

For example: 1 wheat = 2 points, 2 wheat = 4 points, 2 wheat + 1 honey = 9 points. Adding an honey makes each ressources 3 points instead of 2 so that a single ressource addition makes you jump from 4 to 9. Adding another type of ressource will make you jump to 16 for 4 points per ressource. But adding another honey ressource will give only you 12 point (4x3).

If let say wheat and honey gives you more food, it might allow you to maintain more units. Eventually, you will be dependent on this food, when you will lose ressources, it will reduce dramatically the amount of food you receive forcing you to react quickly to patch things up or weakning your army.

Now this bonus could be either given for the whole kingdom or be calculated for each city which would have even more dramatic draw back when a resource type is lost since all cities loose production.