Abhi2410 wrote:

In missile customization we can change its thrusters, load capibility, aerodynamics, range, deployment. These things will increase area and help in making subsonic, super sonic and hypersonic speeds.

We can also make different versions of missile and name. Different version means different range, speed, deployment, etc.

In deployment we can make triad means we can launch it from air, sea and land. 

Missile defence: I want to suggest it to prevent missile attacks with a probability rating to stop attack.

I want nuke or missile should not be immune it should be preventable.

I think that is a really bad idea for a game of this scope.  If it was Cold War Simulator, then it might be ok.    I do think some type of missile defense is a good idea...I think the key feature of how missiles/nukes will work is a recreation of MAD ...where it becomes easy to obliterate another civ, but not easy to stop them from obliterating you.

I always like customization, however adding such detailed missile customization would be very unfair for all the other units and would make Humankind a very complex game for a 4X game... (If the game were a war-simulation game, it would be wonderful feature indeed). so, If we were to add unit customization, it would have to be not-so-detailed system of customization. Here is my humble opinion.

As a part of your empire's military doctrine you may choose a combat role or class of your newly unlocked unit. For example,

-Jet fighter plane
Multi-role fighter (can attack both air, ground, sea target)

or

Air-superiority fighter (can only attack air target but with combat strength bonus)

-Bomber

Tactical bomber (standard unit without any bonus or penalty, mediocre production&maintenance costs)

or

Strategic bomber (combat strength bonus against city defense and outpost defense? and combat strength penalty against units, more production&maintenance costs)

or

Attack aircraft (combat strength bonus against unit and combat strength penalty against city defense and outpost defense?, low production&maintenance costs)

-Tank

Medium tank (mediocre movement point, mediocre unit combat strength, mediocre production cost&maintenance)

or

Heavy-tank (low movement point, high unit combat strength, more production cost&maintenance)

or

Light tank (high movement point, low unit combat strength, less production&maintenance costs)
or

(maybe) Anti-tank (similar to medium tank but with both combat strength bonus against cavalry and combat strength penalty against infantry)

-Field artillery

Indirect support artillery?
or

Direct support artillery?

or alternatively, we might choose by calibre-size

-missile

Cruise missile (short range, can attack units)

or

Ballistic missile (long range, can attack city defense)

and so on...

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Nevertheless, I fear that this kind of system might be already a bit complex. Would the casual 4X players appreciate such degree of customization? That is the question...