Alright, here is all my suggestions and ideas.
1. Stance system. Being able to stand up, crounch and even prone to a command would add a additionnal line of gameplay and tactical choices. Some armor, for example could cost more TU to crounch and prone than others.
I am thinking about a movement system just like Silent Storm. In this game, people can move while staying crounched and prone, but cost a hell lot more TU.
Crounch would be very useful for maximum cover and minimal exposure, at the cost of a high Tu usage and if behind certains type of cover, you could not fire directly in front of you. You could fire trough a fence, but not a rock
2. Explosives should be able to knock people off their feets. Some explosives would be much more efficient than others for this. The explosions itself would of course give some damage, but hitting some objects (Like a rock or a wall) or falling would also cause injuries. Peoples getting knocked back would turn into a rigid ragdoll state over a short distance and then either get back on their feets if they are still alive or stay on the ground stunned or injured.
This is to adress the frigid reaction of people in the first xenonauts whenever they get into an explosion.
3. I am currently studying in 3D game animation. In my personnal opinion, you should have many animations depending on the situation of your soldier. A lightly equipped soldier will have a different stance and movements versus a heavily armored one. People should react and look around when they get fired upon. They should stand against objects when in cover. Whenever you see them in the barracks when you choose their equipements, they should stand around, check their guns and equipements. Depending on their morale and current events, they should look scared, happy, confident, sad, nervous, angry, etc... If they lose a fellow soldier, their expressions could change. If they have accomplished something great or have received new equipements, again, they get different expressions.
4. Make a personality randomly set to each soldier. Some people are serious, some are jokers and dick around, other are very focused on their missions, others are nervous and prudent, etc... Maybe i think too large, but i really like when everything have some life and they just not stand around like robots. This would only affect when you see them in the barracks, it would not have any influence on the field.
5. Better field view and zoom. I don't like the four directions only. Make it at least as an hexa, with 8 directions. Also, being able to zoom out and in would be great to see with more details.
6. External field assets. This could be given when you do some research and under certains conditions. For example, artillery call or even gunship support. Aliens could have similar things.
And so much more...
Your game have infinite potential. I really believe you can make one of the greatest xcom-like strategy-tactical game.