Yeah most resources should be obtainable in more ways than just mining because you got lucky.
It could be through missions, improvements, tech, trade, bazaar, wtv, but has to be more reliable than what it is now.
I'd be all down for some 'important' improvements not costing a lot of special resources (build population or tier2 farms not costing too much if any special resources), but the fancy ones like epiphany (immediately research tech) cost more.