Spoiler 1. When somebody plants mine,it must look a little another.
My idea : Make the mine a little smaller,and covered by tile which it was placed on. (For example,grass - it must be covered a little with grass,stone - it must be covered with a little stone.) And add a little red (blue,yellow) dot that sparkles every 2 seconds. Or something like that.
2. If somebody starts reloading,he must drop the ammo magazine.
My idea : Just a little magazine which drops with the sound of dropping weapon.
3. Shotgun must be reloaded with shells,1 by 1.
My idea : When somebody starts reloading,and enemy comes,he can easily attack with 1,2,... ammo. Make so "Reloading bar" was like this : 1 shell = 0,7 seconds,and then,just add another reloading sound.
THOSE SUGGESTIONS ARE SMALL,but,at leasst they are making the game a lil' realistic.