I think any variant of Silversmith will work, mainly because you start with 0 Silvers.
So it'd be harder to make it overpowered than to make it underpowered.
So the attempt to power it up is to let it gain Silvers, but that supposedly makes it monolithic.
Now what can we do to not make it monolithic and let it be a good card for a lot of strategies?
There are some things you can do, you can give it some +Actions, for instance, you could also not let it gain Silvers automatically, only as a consolation prize, like:
Silversmith$5 - Action
If you have no Silvers in your hand, you may reveal your hand to gain a Silver, putting it in your hand.
If you had one or more Silvers and didn't reveal your hand, Silver produces an extra $2 this turn.
(wording needs fixing, but I wanted to be clear rather than concise for this example)
So with 0 Silvers in your hand, this is just a terminal Silver which keeps the gained Silver.
With 1 Silver, it's effectively just a terminal Silver, worse than Woodcutter.
With 2 Silvers in hand, it's like a Tribute that always gives $4. With 3 Silvers in hand, it's crazy in giving $6!
This is nice enough for BM-decks which buy a good amount of Silvers anyway. It also helps dense engines which can perpetually draw a couple of Silvers. However, it's at that highly competitive price point: $5 and making it terminal doesn't help engines that much. And if engines start to take in a lot of Silver they may find themselves stall too much.
So that's my attempt at creating an interesting card.