Ice Scales stacking with Assault Vest seems like it could be good? I'm testing out a Mirror Coat version right now on a Rain team:
Frosmoth @ Assault Vest
Ability: Ice Scales
EVs: 252 HP / 4 SpD / 252 Spe
Timid/Modest Nature
IVs: 0 Atk
- Ice Beam
- U-Turn
- Giga Drain/Hurricane
- Mirror Coat