I think this is the part that I was questioning, not so much the how. With the ease of travelling between planets, I don’t feel that there is any real distinction between the time it takes to gather materials locally or anywhere else *.
An argument could be made that gathering blocks from higher-tier worlds does indeed take more time and effort to gather and so should be rewarded more, but my understanding of the current system is that ‘exotic’ is defined as any block in a colour that is not available on that planet (hence blocks of the same type from an alternate planet with the same colour do not count as exotic), so no distinction can even be made about whether a block is ‘truly’ exotic, let alone from a higher tier planet **.
I guess at the end of the day the prestige bonus from exotic blocks is already built into the game, and you might consider it a waste of time to remove/refactor it into something more straight forward like ‘Many colours good, few colours
bad less good’.
* Of the same planet tier.
** And I don’t think that system should change, I respect that block-data is at too much of a premium for that right now, let alone in the future.