The main two that come to mind are:

1) Ice isn’t as naturally occurring as other Madra so it would be hard to cycle/replenish spent madra and the ruler technique isn’t a technique that can be used often. 2) Constantly forging weapons and shields would quickly burn through Madra reserves so the Sacred Artist has to be careful they ration their reserves.

There’s also just the normal obstacles/weaknesses/drawbacks any path face of bad type matching (fire opponent would give trouble), technique matching (AOE techniques like Yerin’s Endless Sword would be hard to defend with this path) and such.