Ooh

The timing on this one is going to be kind of weird since the triggered ability will only go on the stack once the spell or ability has finished resolving and hence left the stack and no longer exists.

On the one hand it is "just" a hoser. On the other hand it is a hoser that answers to basic mana bases in many formats - just copying fetchlands makes me want to swap mana cost for casting and mana cost fory copying just so the recurring cost is more demanding.

Those are good points. Is there an example of a card that copies in such a fashion? I wonder. I'll have to try to research that if I find some time. The timing with flash wouldn't work if it copied something on the stack, since by the time you cast it in response and it entered, it would be too late for it to trigger.

I'd have to "leave it to development" in regards to the costs. On the one hand, it's such a niche card that overestimating the costs would make it useless. On the other, it could be very powerful with players using things like fetchlands if the cost were too cheap. Thinking further about it, it would almost certainly appear in a lot of EDH decks. Multiple players with these in play and plenty of mana would through the game into a weird state.