I don't know what size your room is now, but it sounds like the steps are an issue. First of all, is there any way that you could redo the steps so they're not so steep? Or build a landing into them at about halfway? Then, how far is your garage from your house? The reason I'm asking is we're just in the process of building a new garage. It, too, will have a finished room above it that will be my sewing studio. (We're calling it our "garottage" - - garage + cottage). We "attached" it to our house by having a screenporch between the house and the garage. Some say breezeway. It was cheaper than an addition would be but I'll still be sheltered when I go from one area to the next - - I'm from Wisconsin so our weather would be equally wintery at times. Something like that would allow you to continue to use the space that you have that may go unused otherwise.....just a thought.