If the resources were that important, people would put more effort into defending their starbases. Which would be a good thing really.

Besides, it's presently very exploitable - I can buy a bunch of durantium off the AI, build my ships, and then cancel the deal. If I actually needed to maintain that level of durantium for the ships to work (or just for them to be able to repair or some such) then it would add depth to the game.

If a resource was used in maint like it is used for nuclear reactors then I agree ships should have to be scrapped.

If it is only used in construction then like it is.

Well, that's just the point - the way resources work in-game presently only makes sense if they're used for maintenance. I've no objection to a stockpileed system instead, where resources are accumulated and spent; in fact, I'd prefer it. But the present system demands you spend resources constantly once a ship that uses it is built... and then doesn't complain in the slightest if those resources aren't available. 

Strategic resources are just a bit half-baked right now.

Yes, but it can't not happen, either. If you did lose them in the current system then you would have a mining starbase that continued to mine the resource but didn't produce anything...

It's a weird system where resources are treated sometimes like "amount of stuff" and sometimes like "flow of stuff". The result is a hybrid that works as a game limit rule but that makes little sense when interpreted from the point-of-view of the game universe.

You really should separate the "amount of resources" from the "flow of resources". Mines produce some amount per time adding to your stockpile. Building stuff consumes certain amount which you won't get back and/or running stuff consumes some amount per time which you won't get back, either. It would accomplish the same thing but would make much more sense as a description of what's happening in the game.