Poet
+: Apprentice is fun, and this Stockpile/Apprentice fusion should see good use, elegantly tucking itself away when finished with or self returning and cycling for consistent draw.
-: not much of a negative, but it's bad with Coppers; since you really want to make your one-shot count you'll want to get some kind of draw each time.
Overall: Apprentice at $5 is likely weaker than Gold +Buy, but on the other hand, this can get itself back. A thinner and drawer in one card will be strong, but if it's balanced it's flexible and interesting.
Persist
+: I really like how both this and Poet use Exile in a simple but effective new way! Keep buying Persists after the first one and they become one-shot +2 of each bonus.
-: could be too strong. +1 Cards needs fixing.
Overview: balance is the big question here.
Alley
+: Using debt to negate cost reduction power would be nifty, if it works.
-: 'While this is in play' wording has recently been updated to 'while you have this in play'. This needs a lot of $ payload in the deck to do anything, to the point that it will probably be unrealistic and only harmful to the deck.
Overview: with one Alley and 4 Coppers in hand, the Alley takes away the ability to buy a $4 and instead 2 $2s or $3/$1. Any other +buy card is preferential.
With 4 Alleys in play, $8 is needed to clear the debt, with another $8 to get 2 Provinces; again, any other single +buy card would work. Or $5 for 5 Duchies, which might be more valid.
8 Alleys in play needs $16 with it. By the time you build the deck to get $16, is there the time to get 8 more stop cards?
So, buff it somehow. Reduce the debt to 1, or even stick +1 Card on.
Servant
+: The reaction can open up new and interesting strategies.
-: the reaction window is narrow, with there being few choosing cards. The self synergy is quite weak (as I feel it should be) with potential Lab or +2 Cards + $2 across three cards in hand.
Overview: it feels like Patron, rarely good with its reaction but fun when it is.
Another 4.