1. Any link antenna at a high elevation will likely be low on the tower, if not on the shelter itself.
2. Circular (preferred) or horizontal polarization should be used instead of vertical.
3. A circularly polarized antenna is much more easily protected by a (homemade) radome, which should be black for UV protection and faster snow/ice melting.
4. Direct, and especially falling, icing and/or snow loads, along with wind, will be a problem - more so with a corner reflector or horizontal yagi-uda.
5. A corner reflector on a tower or monopole is more likely to have its azimuth and/or elevation accidentally changed by a climber. (Now what was the original orientation?)
6. A digital link adds complexity and, for retrievable intelligence, has to always be of sufficient strength, probably requiring more power and/or antenna gain than analog to maintain link reliability.
7. An analog link is much more forgiving of temporary/seasonal path loss, allowing intelligence during a reduced circuit merit resulting in less than full quieting. An analog link should always have analog tone squelch rather than digital squelch.
Mike WB0DZX