You can't use any TV antenna components, they are all 75ohm impedance whereas two way radio uses 50ohm.
Stick to simply swapping your antenna elements if you are moving through such diverse terrains. If you start with a 100% of signal, every metre of cable will cause loss, splitting the signal between two antennas likewise reduces the signal to and from each antenna. Even a two way switch causes some loss. Better to have one antenna working at maximum efficiency.
I find the 6dB whip is the best all rounder. I can communicate quite a few kms on the flat and in the hilly country its largely line of site.