i don't think the mechanics of flying the plane would be any good for just one mission in Africa 6...
You're probably right there - nowhere near IL-2 levels of simulation, that's for sure..
That weapon crate texture was likely a predecessor of the gun-bags. Frankly, I feel the gun-bags work fine as they disappear dynamically to indicate what's left in the box. That particular texture would make it very hard to do so.
The MG's would have been very cool, but I doubt the devs at this point in time had progressed 'deploying' much beyond 'you can only fire while prone', and otherwise the guns would be no different than the Bren. Still would've been a nice addition, though.
Flamethrowers also would have been cool, although I'm not sure how well H&D2 would have handled them, especially in multiplayer. Bear in mind, this is a game that cannot handle variable detection ranges on dedicated servers, let alone dynamic, possibly spreading, fire. I definitely feel like the flamethrowers were a good idea had by the devs as production began, but were scrubbed when they realized how difficult they would be to program.
With that said, one thing I thought of a while ago - I have no idea if this is true or possible - is if the item id's for the MG's and Flamethrowers still exist in the game code, would it be possible to use these to add completely new weapons into the game without replacing existing ones? For example, adding an M3 grease gun in lieu of the absent MG34, and using it in a mission. Again, I have no idea if this would work, but it would be something to look into.
Some unused icons:
As stern said, the canister icon is actually a German gas-mask canister. Possibly a replacement for the German backpack?
Some of these icons indicate to me that the devs were possibly looking toward a 'Death to Spies' approach to some missions. The German book and notes would likely have been documents required to carry or acquire, while the hammer looks like a good candidate for a melee weapon which would not arouse suspicion under certain circumstances.
The chocolate and cigars are what really confuse me.. Possible easter-egg/hidden objective?