I’m really sorry to say this but there are just too many ‘challenge mode’ ideas in the forum. I do understand the need for a more challenging gameplay experience since many of the veterans here think that even SSH is too easy (most of the time). But keep in mind, there will be difficulties even higher than SSH, so those difficulties might be what you’re looking for. And if even those difficulties aren’t enough, I still have a major gripe about this idea. Basically you’re only making the chickens a lot tougher, which is far from the ideal way to increase difficulty. Making bullet sponge enemies is a less effective and more irritating way of increasing the difficulty. I would instead increase the frequency of enemy attacks and the speed of enemy projectiles. You could also increase the likelihood of epic waves appearing in the mission.
This is what I think of your idea, a rather unoriginal and flawed idea. I’m really sorry Bored Celestial, but I really feel like you missed the mark here.