since both unupped reverse time and the hourglass ability cost are 2, 2 would be a balance cost in my mind as it does either or.
Bear in mind there's a -1 to quanta cost due to the nature of the Lucky! Series mechanic (50% chance of achieving the desired effect).
I would not assume a -1 quanta cost. If both effects are worth N quanta then you will get N quanta out of each use.
As I said before
Reverse Time is worth 2
+1card
Precog's draw freature is worth 0
+1card
Therefore the unupped is worth 1
+1card (how it currently is)
However
:Draw a Card is worth 5 (see calculation below)
:Reverse Time is worth 7 (see calculation below)
Therefore the upgraded is worth 6quanta. (subtract 1 for the upgrade bonus and it should cost 5
)
Therefore the casting cost or activation cost should be increased by 1 for the upgraded.
Calculation mentioned:
Activation Cost Modifier
AC/Mod
1/+1
2/0
3/-1
Draw a card Calculation
Golden Hourglass
4 (Cost) = 4 (Skill Value) +0 (Activation Cost Modifier)
: Draw a card
5 (Cost) = 4 (Skill Value) +1 (Activation Cost Modifier)
Reverse Time Calculation
Weapon Cost = -3 (unique card slot) +Attack +Skill Value +Activation Cost modifier
Eternity
6(Cost) = -3 (unique card slot) +4(Attack) +6 (rewind) -1 (Activation Cost modifier)
:Rewind
7 = +6 (rewind) +1 (Activation Cost modifier)
In summary:
Casting Cost 1
|4 or 5
Activation Cost: n/a|
or