Is there an option to grow the Attack by time?
when play with K2 in Rocket Mode, which is full tech at the begining, the enemy is too strong at first wave, and it's less danger after that wave

The number of biters in the squad grows with evolution.
Also, launching a rocket increases the size of squads.
At the moment, there is no increase by time.

However, there are plans to gradually increase the squad size up to 20 units over time if the evolution is too low. However, don't expect it anytime soon.

Also, high-tech K2 has a strong advantage over the default biter level (5).
Biters will have a chance only due to the fact that resources may run out, or the player will try to save on defense.

If the player did everything right, then they have no chance.

Biters have chances at max level = 7. The ninth is likely to kill the player.
What can hold a max level = 10 - I don't know )

Yes, I'm using the biter level 6 in rocket mode, and 45 min peace time (also lots of setting to weaken the first wave). the turrent is very strong after full-tech.
but for noraml K2 in mid-tech after launching rocket.
the biters are bit too strong and always attacking and I can not defense my external resource base even with 50+ turrent

Another question is, Can I create a mod to change the biters's squad size? How to achieve that?

I want to create a mod that can increase the biter's strength by time (in about 5-10 hours game play time)
also some random dice to roll mutation about the biter's ability, (like poison, nuclear, inferno, size, hp, etc..)
I think that would be interesting, also I'm recording videos about it.
Also it could be great if you add this function in your mod

The current squad size is an internal mode variable. Other mods, without special permission, will not see it. In addition, it is recalculated once a minute. I don't see a way for another mod to change it.

Regarding the random mutation - it already exists. In the late game, once every 10 minutes one of the biter "bases" mutates randomly. Usually, this is a change in the ratio of factions within the base, but stronger mutations are not so rare. Including with a complete change of the genome. Another thing is that the number of "bases" in the late game can reach a couple of hundred and the general situation on the map changes quite slowly.

However, if it will be useful, you can execute the command "/rampantForceMutations". This will cause all bases to mutate immediately, and in about 5 minutes all nests will change. During mutations, there may be a noticeable drop in UPS

OK, then, Can I disable or enable tiers of biter at runtime, say, I want to disable poison at begining and enable it after 1 hour.

Yes. You can definitely allow a faction later if it has been disabled.
Disabling a faction is more difficult. First, the nests of the disabled faction will be deleted from the map. Although no one complained, I suspect that if you disable a faction that participates in an underground squad, then there will be an error when trying to unburrow. If there is such an error, you will have to disable underground attacks.

Also, it is worth knowing that at the beginning of the game it is impossible to get factions of tier2 and higher. They appear as evolution increases. Poison is tier 6. Approximately 55% evolution

That's nice.
I searched your code and found there is a Interop.lua seems the interface operation, but seems it has been comment out, so how do I use your remote interface.
Also another Idea is that you can spawn Giant biters after some time.

Also I've disabled underground attacks, I think it's a bit annoying and as rocket rush is a small base, I have no room to place turrent inside the base

The remote interface is commented out, because in the process of reworking Rampant, only the "core" remained from the original mod - namely, the collection of data about the map and the constructor of objects on the map. And the code in the interface is outdated and non-working. You probably won't be able to use it