1 - You can define deployment orders for your crafts as part of the ruleset. (Dioxine gave a good description of it here:
https://openxcom.org/forum/index.php?topic=2808.msg30741#msg30741). The game goes down the list and places soldiers on the coordinates you defined in that order.
Otherwise the default behaviour is to start from the north-west-most corner of the craft and fill it from there.
2 - I suspect that the pile of stuff goes where the first deployment tile is. Which means that it will always be where the tank is, but if you change the location of the tank, that should change to location of the pile of stuff too.
Conclusion: Write a deployment entry for your skyranger, starting from the middle of the craft, then fill the rest of it. Both the tank and the pile of stuff should be in the middle. It will be annoying at the beginning of the game though, since the first soldier selected will be unable to move, stuck in the middle of the craft.
Also, I like the tank being first because it is the best at resisting the damage (and if I lose it, I don't lose hard earned experience, just a tank I can rebuild), but play styles do differ.