Whether the spokes still have life left in them or not, this whole project hinges on being able to unscrew the nipples. Living in WI I have not had good luck disassembling old wheelsets. In most cases the nipples are so frozen they round off or the spokes break trying to remove them. At that point the remaining spokes get cut and I start with fresh ones.

Before doing too much planning I'd give each nipple one full turn loose to see if they will move or not.