I thought of a way to fix it!
[some card]
Action
$2P
+2 Cards
Choose one: +$2; or, +P
Of course, the other things could get changed, but I decided to get rid of the +action because you could easily stack these and get the $6P necessary for the possession pretty easily.
Also, I randomly thought of another version of the traveling merchant that might be better:
Traveling Merchant
Action
Cost: $2
+1 Card
+1 Action
When you play this, return it to the supply.
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When you buy this, if you have not bought a Traveling Merchant this turn, choose one: +$3; or, +2 Buys, +$1
I was wondering which one I should have it be, give you an extra buy or more coins, but I thought, why not do both? The "if you have not bought a Traveling Merchant this turn" is to keep you from piledriving them all by repeatedly buying them and getting the extra buy, then the extra coin, etc.