I bought Xenonaughts last week, and already spent 30 hours playing - I'm really enjoying it.
However, I find the way grenades work to be a little frustrating, to say the least. I've no idea how one supposed to play Ironman mode, when an attack on alien base can end when some alien decides to throw a grenade at you. And suddenly, your soldier(s) is(are) dead instantly and there's nothing you can do about it, besides just watching them die.
I have a suggestion for the second game, that may help with this.
What if there was a mechanics that allows units to take cover from frag grenades that land under their feet - if a unit have enough reflexes and some TU's left, then similarly to reaction fire, they can spend those TU's to automatically run away from the explosion. This will help against enemy grenades, and also can be used as a tactical move - throw a grenade at the aliens, who huddled in a corner inside UFO, they try to run out (because obviously no one wants their legs to get blown off), and expose themselves to fire.