1. Well, the thing is that you have a very small line of defense. Being a sniper would require you to remain unnoticed. If you'd place a sniper in a sandbag bunker it would make the sniper completely useless in practice since he's spotted and shot at before he can actually shoot. So that's kind of why we decided to let you be the only sniper on your team, covering your soldiers from the far back. The precision your riflemen shoot with gets pretty close to sniper quality after a few levels.
2. That's what they're for, to annoy you. MUHAHAHA. No really, I added them because they keep you busy and focused and add a nice different element to the game. I kinda like them myself and the way you have to build roofs to protect your soldiers from them.
3. Grenades are just too much work for now. It would require a real load of additional animations. I just don't have the time for it at the moment. I'd rather keep that in mind for a potential sequel
If you have some small cool suggestions that can easily be added don't keep silent. Stuff like what Ikarases suggested can be added quite fast and doesn't take a lot of time, because that's the one thing I'm very short on at the moment.
"The absence of rules is the enemy of art." ~Orson Wells
