I don't see the problem in having to make an industrial blast furnace (ignoring all the other methods of obtaining steel). If one is playing with GT, one is going to be making one sooner or later and the standard casings are reusable in other multiblock structures as one replaces them with reinforced casings. Supplying the power is as easy as putting together an mfe and charging it up (which can be done with a single generator over time if one hasn't bothered with a power infrastructure). The recipes even tell you how much total power you'll need for the full run.