I love the general concept. I think its definitely something that should be considered. While I haven't gone through the numbers, so I won't opine on those, I will say that this is an obvious win.

I think the only 2 objections will be:

1. what are the ratios to make sure the cards don't have unintended consequences (that's a negotiation imo, not really an objection).
2. this will take up too much DEV time to make. I think it could be streamlined in a v1.0 rollout (like how the voucher shop started); and then in the future it could get way more cool.

I feel that this could appeal to 3 types of players too:

1. the ones that like unique and interesting cards to play in a very niche spot (so definitely not OP but they should still have something to offer for regular gameplay - even if its infrequent the card would be played)
2. land owners that want more production for their land game
3. card collectors that like the opportunity to have unique collectables in their portfolio.

Great job @dejota and thanks for the tag @bjangles :)