This Card:Exchange::Rogue:Graverobber
I like it. Definitely include this if Axeman proves too strong and you go back to "Magistrate" (or whatever you renamed Tax Collector). Even if it hits Silver, you have the Silver ready to go and therefore this card is a Silver with a bonus (the oneshot attack). An analogy that kind of works for the cards power is a Silver with a Trade Token that you can use for a one time Knight/Saboteur attack - you lose the versatility of the Trade token but you gain the versatility of what card this might turn out to be. It's kind of like turning the Trade Token/Fund theme on its head - you don't quite know what card it is you're going to get, but you know it has a very nice one time use effect. Perfect for the set.
The interaction with General is slightly worse than the interaction with a KC, so no issues there, although it may be worth an "if you did" wording. You could even flip the "if you did" wording so that you don't have to trash the card if the attack "misses", or to add a bit more choice. Eg:
+1 Action
Each other player reveals cards from his deck until he reveals one costing from $3 to $6. You may trash this. If you did, each other player trashes that card. He discards the untrashed cards. Gain a card trashed by another player, putting it in your hand.
So the card's a reverse sage attack (weak) until you find a card that you want (very likely).
At any rate you'll need to make sure the wording is clear that you can't gain the Takeover you just trashed, or else it's a deck nuker.