There is no single correct answer when it comes to picking supports and choices depend on playstyle and what you're currently attempting (typically boss farming vs. map clearing) as well as other gear choices. For example, if you can get frenzy charges without ice bite, you might want to take something in its place.
Cold penetration works but because only 60% of the skills damage is converted to cold it already loses some effectiveness (I didn't think about this part when posting my comment). However, you can get full benefit by taking the "Winter Spirit" cluster in the tree near the ranger starting spot. This will give the other 40% conversion to reach 100% cold. This also allows for a weapon elemental damage support (35-54% more damage compared to faster proj supports 20-29% more).
Ice Bite helps the most if you are just doing general map clearing as you will continually gain frenzy charges which give movement/attack speed to get around faster as well as increasing damage. The flat added cold damage per frenzy matches the damage from an added cold damage support at around 7 frenzy charges. Even if you have less than 7 it still has the additional benefit of granting frenzy charges (in turn granting speed and 4% more damage each) and freeze chance.
Hypothermia is interesting because its damage works in both scenarios (assuming Ice shot as main skill) because of the chilled ground it creates on hit. Since it has less single target damage and doesn't grant frenzy charges it is not as good as a first option as the others and I honestly wouldn't take it at all considering other options available.
Other suggestions would be added cold damage, physical projectile attack damage, greater multiple projectiles (replacing lesser multiple).
