So... I tried to work around what felt like awkward wording and came up with a funky scenario instead. Let's peel through this.
Question: what counts as "card draw?" Do cards drawn with Library, Scout, Apothecary, Scrying Pool, etc. count?
Library: This interaction was intended to work, but it just doesn't since you aren't drawing a set amount of cards. First big reason to change my card.
Scout: Scout doesn't allow you to draw cards at all, so it isn't a problem. The +1 Action is still replaced.
Apothecary: Same as Scout, except for the initial +1 Card, +1 Action.
Scrying Pool: Same as Scout.
Council room, Festival : give +$5
Conspi+Worker's village : +$4
Shanty town : +$4 or +$2 depending whether you've actions in hand or not.
...
OMG ! Play LC + a cheap card, transform the cheap card into "more than a gold".
And what about duration cards ? If you play wharf after LC, do you get +$3 this turn and the next ? And if you play LC+Throne Room, +king's court, does it apply to the card you play twice ? (yes, I think it rather applies to Throne room and it gives $0...)
Duration: If I recall correctly, the rules say a Duration card gets played this turn and your next turn. That's why it can work with Conspirator on the next turn. If that's true, Lost City + Duration only replaces the events the first time.
King's Court: If you King's Court a Lost City, you'll end up with +1 Card, +2 Actions, and +$6. The first replaces events on the second, and the second on the third. You'd also get coins from the next Action card you play.
Library? Farming Village? You don't know how many cards you'll draw until you actually draw them. Minion -- do other players get +$4 too? I'm sure you can come up with answers for these and whatever other questions I might pose, but the problem is that I have to ask in the first place. This is a rules nightmare. Even if you manage to make it work somehow with the current cards, it's easy to imagine perfectly reasonable future cards that it wouldn't be able to untangle.
Library: I covered this above. It's the one mechanic that makes me need to change this card.
Farming Village: Same as Scout and all the other examples above. These cards don't "draw" anything. They "put (a card/cards) into your hand." There's a real difference between the two.
Minion: If you choose mode two, you discard 4 cards, then get +$4. Your opponents just draw cards. This is covered by the word "you" on Lost City.
Most of these situations have reasonable answers. The game mechanic of replacing one thing with another
can be complicated, but it doesn't have to be. The only real problem posed was the Library issue, which is a real problem since you'd just draw forever in this combination. Here's a new wording (and I welcome help on how best to present it):
Lost City (5)
Action+1 Card
+2 Actions
Replace each instance of "+ Card", "+ Action", and "+ Buy" on the next Action card you play this turn with an equal amount of "+ $".
I'm not sure if I should put a variable in there or not. I was also thinking about making each instance a "may"; that is, if I play Worker's Village, I could replace three things with +$ and leave an Action or Buy left over. Normally, I like forcing players into working as best they can within a card's confines, but this seems like a good situation to cut some slack and allow craftsmanship to take over.