From the small amount of playing, I'd say that if you liked the lore and art of X1, you won't be disappointed with X2.
I would also love to see JA2 style things in ground combat, but without any developing experience with xenonauts, I'd say that many things like idle animations in JA2 combat are impossible to do in Xenonauts without huge rewrite. But maybe something can be done e.g with mods later.
Some of the things I would like to see are:
- Prone stance and crawling
- Alien bleeding and panicking (maybe this is already done?)
- Blood trails and foot steps so that you could see where alien went hiding
- Aliens hearing shots and reacting to them more or less intelligently
- Hit locations with more or less damage according to location and possibly with additional effects like blindness, halved movement rate, reduced accuracy or throwing distance, etc
And then there is one big thing, more like wishful thinking, that would make juggling with soldiers more interesting, and that is soldier relations between each other. It didn't need to be as deep as the relations are in JA2, it could be something simple instead, like that soldiers that have gone through several missions together in the past would e.g get bravery or reaction boost during missions. On the flip side they could panic easier if their long time buddy dies.
One thing I know is coming, is different head gear. There is already re-breather for smoky situations and tactical visor that gives some bonuses for the wearer. In same way something like night vision could be implemented, if not in the game itself, then with a mod.