Okay here's the structure I hope I forgot nothing:

Different core-mechanics regarding realtime/turn-based:

• Round-based building, after that the towers fire simultaneously depending what angle/velocity you chose.
  Defending towers start automatically to intercept incoming missiles.
• Hybrid-mode: you fire in fire-phase in realtime rather than give commands in build-phase. Defending turrets are still automatically fireing. Maybe with something that prevents the player from attacking too soon.
• Full realtime-mode: no different phases, you can shoot as soon as you are able to do so. May be less tactical because of the lack of different towers etc. because I am not able to fill the game with diversity (I want to compensate this with a great mechanic ). I worry that every game is the same after you once have a working build-order.

Are there other core-elements that make the game more interesting? Something that demands more dexterity/skill? I worry that it will become boring because it may be too easy to adjust the towers.

Now, after I restructured all these great ideas you got we can think more precisely what are the weaknesses of these concepts.

Ha, I guarantee we're in feature creep right now... I think it's just as important to pare down until you have what you want the core gameplay figured out.
Turn-based vs Real Time definitely fits into that "core" so I would consider the advantages/disadvantages of each before making a decision.

This really hits what I wanted to say. I want to have the game as big as it's possible (this is why I asked for example for special-power ideas, they are easy to implement), but I don't want the game to have a boring gameplay with logical trouble (how do I make every new game unique?) but 100 different ammo, tower, etc. -types.
I want to pare down the diversity. Not because I'm lazy, but because the core-mechanic is much more important.

Thanks, Phil

Okay here's the structure I hope I forgot nothing:
Round-based building, after that the towers fire simultaneously depending what angle/velocity you chose.
Defending towers start automatically to intercept incoming missiles.

Towertypes: cheap with light ammo, medium with medium ammo, expensive with heavy ammo -> can be upgraded in shot interval etc.
Factories: Ore gathering unit, Ammo producing unit, Active Tower producing unit, Passive Tower producing unit
Special abilities you buy once and affect the fire-turn: doubled velocity of missiles, field that slows enemie's missiles down, make enemie's base visible, launch nuclear bomb

Alternatives:
Hybrid-mode: you fire in fire-phase in realtime rather than give commands in build-phase. Defending turrets are still automatically fireing.

Full realtime-mode: no different phases, you can shoot as soon as you are able to do so. May be less tactical because of the lack of different towers etc. because I am not able to fill the game with diversity (I want to compensate this with a great mechanic ). I worry that every game is the same after you once have a working build-order.

Now, after I restructured all these great ideas we can think more precisely what are the weaknesses of this concept.
Thanks, Phil

Edit:

Ha, I guarantee we're in feature creep right now... I think it's just as important to pare down until you have what you want the core gameplay figured out.
Turn-based vs Real Time definitely fits into that "core" so I would consider the advantages/disadvantages of each before making a decision.

This really hits what I wanted to say. I want to have the game as big as it's possible (this is why I asked for example for special-power ideas, they are easy to implement), but I don't want the game to have a boring gameplay with logical trouble (how do I make every new game unique?) but 100 different ammo, tower, etc. -types.
I want to pare down the diversity. Not because I'm lazy, but because the core-mechanic is much more important.

Okay here's the structure I hope I forgot nothing:
Round-based building, after that the towers fire simultaneously depending what angle/velocity you chose.
Defending towers start automatically to intercept incoming missiles.

Towertypes: cheap with light ammo, medium with medium ammo, expensive with heavy ammo -> can be upgraded in shot interval etc.
Factories: Ore gathering unit, Ammo producing unit, Active Tower producing unit, Passive Tower producing unit
Special abilities you buy once and affect the fire-turn: doubled velocity of missiles, field that slows enemie's missiles down, make enemie's base visible, launch nuclear bomb

Alternatives:
Hybrid-mode: you fire in fire-phase in realtime rather than give commands in build-phase. Defending turrets are still automatically fireing.

Full realtime-mode: no different phases, you can shoot as soon as you are able to do so. May be less tactical because of the lack of different towers etc. because I am not able to fill the game with diversity (I want to compensate this with a great mechanic ). I worry that every game is the same after you once have a working build-order.

Now, after I restructured all these great ideas we can think more precisely what are the weaknesses of this concept.
Thanks, Phil