I've been trying to make green joker work, but not even in a niche scenario seems to fulfill an 8 ante run.
So I'll suggest the following:
+ Green joker
+1 mult per card scored
-1 mult per discarded or destroyed card
That way, green joker can benefit from poker hands that score more cards and can be tricky to grow at early antes with low to none deck fixing, keeping in mind that destroying cards takes mult, that makes it so green joker is good for early and mid game; you can risk it and play any hand you have available without discarding and not getting a strong enough follow-up.
High risk, high snowballing if everything goes right! (Now, in practice I don't know how this would go 😅 )