I can live without IC2. It would be a welcome addition to me, but it isn't really needed.
However, I would still like to see BC, as it improves Railcraft. You can use steam better, transporting it over larger areas. The pipes are the main reason I would like to see that in, and Railcraft (As far as I am aware of) is modelled with BC in mind.
But then again, it would take away the uses of rails, making rail craft kind of useless. Basic Pipes mod isn't user friendly, the tanks are very confusing and I can't get them to work, and the TMI mod didn't help with finding out the recipe for an Iron tube. Would love it if Steam Power updated a bit and made it a bit less confusing.
Also, am I the only one wondering if Steam powered carts will be added? Lol