As per logic, when a frozen troop is burned, it should remove freeze. This is because, in reality, the flames would melt the ice, allowing you to move freely again, but still seeing that you feel the effects of immolation. Likewise, if a troop is on fire, they should have immunity from freeze. Maybe a new status effect called “Cryostasis” should be implemented as a gel of Freeze and Burn; immobilizing troops after 4+ moves, but also dealing 5 damage over time per turn since it is a deep freeze (or an ice burn (OR a freezer burn)).
I would also like to see burn revert the confines of entangle, since the fire would disintegrate the vines.