On scouting ahead. I agree this would be the only reason to unmount from the tank. Unfortunately, being hull or even turret down isn't always an option. Think about forested maps, or if you want to go around a building without exposing your tank.
For this reason, I'd like to see ONLY the commander be allowed to unmount, and if the tank gets blown up, they respawn with the tank. Of course no cap power for the unmounted commander. Maybe I'll put this in the suggestions.
Hmmm, gotta say I'm not really in favour of this. If tankers see the commander pop out and scout ahead they might think "WHY CAN'T I DO THAT" and flood the support forum with complaints. IMO it's either the entire crew stays locked inside or all of them can exit.
It's true that you can't scout around a building but I imagine that most maps that have tanks as well as a lot of buildings will be combined arms. So the infantry can do the scouting ahead. That's the whole point of combined arms - the tank can't survive without the infantry and vice-versa. Besides, leaving your tank makes you very vulnerable, especially on combined arms maps. You can get killed very quickly by leaving the safe interior of your tank, and if that happens your tank is just a useless tin can (except when there are still human players in the tank, but as I wrote, the pros of the new system outweigh the con).