cw8: Played the demo, not really persuaded by it. Are there going to be more fire modes like in the original, aimed, burst etc?
It looks like all soldiers get a basic shooting skill, and special fire modes will depend on perks and abilities unlocked.
What's engineering for, do we get to manufacture our own weapons and armour?
Of course yes.
Will there be a market to buy and sell stuff like in the original?
Yes.
I noticed when I promoted the soldier in the demo, he automatically gets a rocket launcher, tell me that that is a demo thingy, will the actual game require you to equip all the soldiers by yourself provided you have the weapon in the first place?
Rocket launcher is a skill for heavy weapon specialist unlocked by leveling up, it's not for everyone. The gear and equipment should have some degree of customization, but I bet most of it will have class restrictions.