An alternative to bigger raids ?

[carbon]

I intended the "slow-and-steady" idea as a rare late-game enemy offensive when bigger and bigger raids get rather dull.

I wasn't trying to make killboxing obsolete, it is simply that the "slow-and-steady" raid idea would be useless against a killbox, since there's effectively no chance of it being overwhelmed and the colonists could spend the entire time having tea and chocolate. Making it not useless would require some countermeasure or other. I gave 3 possible options. The alternative (i.e. no countermeasure) essentially pushes the players -toward- making killboxes since they are so effective against this raid type.

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Also, if you really need more RP-ability, lower difficulty settings always allow for that. No hardened defenses needed.

I get by fine on turretless Randy Intense with 20 - 30% pacifists who can do repair and healing work during combat. I'm sure going to higher percentages is fully viable at lower difficulties.

[Sinosauropteryx]

* a raid + manhunter pack

This is the most intriguing to me of OP's suggestions, and I think it could really spice up late-game tribal raids while giving them more of an identity beyond "big low-tech mob."

Consider this possibility:
"Manhunter Raid! A group of tribespeople from the Orange Duck Taxabobico have arrived. They have brought with them a trained pack of maddened boomrats. They are attacking immediately."

The animals would not attack the raiders, but otherwise they'd act like a manhunter pack. A colony that usually shuts its doors and waits out a manhunter pack will have to contend with the tribals breaking down the doors.

Flavour wise, tribals are already somewhat associated with animals. The Lost Tribe scenario starts with three pets instead of one, and the tribals themselves have animal names. Colonies often keep packs of battle animals, so it makes sense that tribals would do the same. And it would give them something distinct and special to do that pirates don't do. Like a tribal version of the siege/sappers.

[O Negative]

Raiders with trained attack animals (rhinos, elephants, boom-animals, wargs) gets a huge +1 from me. Although, there needs to be a red name under the attack animal, just like with the raiders, so they can be discerned from colony animals.

I'd be interested in seeing Mechs with long-range EMP weapons/mortars in the late game.

All in all, bigger raids over time is (as others have already said) incredibly boring. It's interesting to read some of the ideas people come up with here.