Your current set up is a lot like my present one. I took over my daughter's bedroom when she moved out. I also have a closet and a half bath. The room also houses our computer set up. I purchased two four foot folding tables from staples and made myself a sewing set up. One table faces the entrance, bath and closet. It holds my sewing machine. On a small "night" stand I have my serger with it's back to the outside wall and then against the backwall of the room and parallel to my sewing machine table I have another 4 ft. table that houses my two embroidry machines next to one another. My husband the machinist, cut the legs down on one of the tables to just 27". That makes it the perfect height to house my sewing machine at the right height to be ergonomic for me personally. The other table we left at it's original height as the embroidery machines you just load and turn on. I use the space under the taller table to house a lot of plastic storage drawers in their own rolling carts. I also have one under the sewing table at the far right end where it doesn't inhibit my using the foot control. I use a small tallboy dresser with the feet cut off as additional storage and a cutting and ironing surface for small projects or little things. There are shelves on adjustable tracks on the walls behind the embroidery machine table and over the cutting and pressing area. I even have wire racks like you use in the kitchen for foils etc hung on both sides of the cutting station to house my freezer paper, various stabilizers, pressing cloth etc. I also got myself an office chair from Staples that makes sewing at all three stations just the spin of the wheels. Some of my stash is in the room in the dresser and the closet but most of it is downstairs in my basement in a backroom that was a bedroom for my step-son at one time. It is now full of my rolling ironing station and my large cutting table. Each of those also provides a lot of space underneath to store fabric etc. I also have plastic shelving placed two deep that holds multiple bins of fabric, notions etc.
At one time my sewing/computer room was two small bedrooms. We knocked out the dividing wall and added the half bath when we were down to just two children at home. It was actually our master bedroom for a couple of years. We then built a seperate bedroom on to our home for our master. Since our nest was completely empty once our youngest graduated from college and got a job to far to commute from here we have had it all to ourselves. I did have my entire sewing set up in the room where I have my stash in the basement for a little while. There can be a dampness problem and heating is also an issue. We use a woodstove to supplement the heat in the basement familyroom but it doesn't help much in the back sewing area.