Looking at the spell progression and I noticed that Frost Scythe has no upper tier equivalent. But, that's not really a problem since the spell is such a good "grows with you" spell (and while not a prereq, Rimefang works well as FRS' big brother). I did however have an idea to broaden FRS' usefulness.

Shape Ice (SI):
Held mana spell.
Cast the spell and hold mana and you can improve the stats of a frost scythe in your hand.
RUB scythe - increases slice at the cost of impact.
PULL scythe - increases puncture at the cost of slice.
RUB water on scythe - increase impact at cost of slice/puncture.

It's basically frost scythe forging. The more mana you hold the more effect it has. So, you can hold a large amount of mana at first then release down for minor adjustments.

The Crystallize Ice Cantrip would be used to "seal" the changes. You must make the adjustments before casting that cantrip, so you don't have all day to fiddle with it.

As a bonus you can use the Shape Ice spell on snowballs for a little ice sculpting fun.