I don't understand how adding a "build time" to placing defensive structures (and maybe other structures too) would negatively impact base defence. It's a simple solution, and wouldn't change much else mechanically.

Another option would be to make laser turrets require batteries be placed in them ...

Really excited to see that you are going to take a look at the combat systems of the game - they are for me the weakest part of factorio in it's current form.

I was playing around with some ideas I was thinking of making a mod for that would address this very thing.
1) Create a few more enemy types ...

+1 to this!

Right now it requires a burner value in the car entity prototype
It is not currently possible to create a vehicle type that either relies on the equipment grid for power, or doesn't require any power source at all.
I would love to see new energy source options (so that mod creators could add new ...

> Liquid sands

What you're describing sounds more like ice than sand - the player would slide when on ice.

For liquid sand... quick sand... the player would sink in it. I can think of some ways to do this, by putting entities over the quicksand patches that would give the effect of the player ...

Maybe I just haven't come across it, but I would love to see a mod (or the vanilla game for that matter) do something with the alien concept that actually felt like it took from what the alien behaviour and organic nature lend themselves to.

Ideas:

a) "Organic" Facilities - Structures you "grow ...