Personally I see little point in cluttering sgminer sources with OpenCL kernels from a dozen of altcoins, but there's nothing preventing sgminer devs from integrating my changes. Ask them, not me.

No idea, they were already present in the original sgminer.

It's possible, but involves too much work to do it just for fun. The sad truth is that people are mining loads of coins with this software, but I can count donations to the project on my fingers. Organize a solid bounty and I may reconsider.