I think to better understand what you are asking for, you need to know how the game handles Oil and Raw at the moment.
To do this, you have to know about RegimeSlots. Basically these are variables that can be any number at all. You can have an event add, subtract, divide and multiply them with anything. And they are easy to use in coding events. Oil and Raw are RegimeSlots. Now RegimeSlots can be alot of other things too. For instance, if you want to make a timer for a specific nation, that counts down each round of play that is played, you can make that as well. Or you can use them as a boolean (true/false) to set any number of features for a specific regime.
When a location, like an Oil Well, produces oil, it does so by producing an item. This item can be set to be a RegimeSlot. So, an Oil Well, will produce oil, by adding the number (of items) produced by the location to the RegimeSlot.
This is NOT what happens when you produce supply. Supply is handled by the game engine, in a different matter. It is NOT a RegimeSlot.
So changing Oil and Raw to be Supply like is a bigger undertaking, that would need to update the game engine, and probably by adding to the supply function, which already can take minutes to calculate in scenarios like WaW for ATG.
You might argue that you could make the function that needed to be added to the game engine a little simpler than the supply issue. You could argue that you wanted to check if there was a "connection" between a resource production site and resource "recieving" site. But that too would be awkward. For one thing, what is a connection? Is flying good enough (over enemy territory or not)... Surely for some resources such as "diamonds" or "cash" (which i operate with in my upcoming Congo Scenario) this could be done. While for other resources such as Oil and Raw, this would be bad. Also is moving the Raw/Oil by sea going to be viable. How do you explain that supplies donīt get through, but Oil and Raw does?
Also there is the matter again that each resource is a RegimeSlot. What to do about all those RegimeSlots that are booleans, or counters, or something else? Clearly we would need something different, perhaps a RegimeResourceSlot for each country. And what then? What about all those scenarios that would need to be reprogrammed to update this new ResourceConnection check?
All in all, this is going to be alot of reprogramming for something that the game already supports, albeit a bit unrealisticly, at the moment.