I've been reading your thread and share your joy and fun in the wintertime, planning for the spring trip(s). I was looking at your picture of your packed horse and you comment that all extra you needed was extra clothes and food. You'll need a fuel bottle for your stove. Sewing kit and spare clips for when (and not if) the plastic clips attaching your saddlebags breaks. Or spare ďropeĒ or leatherĒreinsĒ for the same need. Are the saddlebags waterproof? If only water repellent, you'll have to pack up everything in plastic bags or what do you name it in English, pack bags? You'll need fishing gear for the trouts you are planning to catch. First aid kit for you and the horse(s). Toiletries.
How are you planning to camp the horses at night? In a portable corral? It takes up quite a lot space on the horseback too and adds weight. Highline? Picket? Are your horses used to be hobbled? Picketed? Are they shod or will you use boots or let them be barefoot? If they are shod you'll need an extra front and back shoe and tools to put on shoes. Or a spare boot.
My point is that it all adds and takes up a lot of space and it isn't easy to fit everything onto the horse even if you plan all the meals to be instant and don't even bring a single bread!
I do absolutely not mean to dis encourage you, go out there, camp and have great fun, you will learn from experience and it is fun to go camping with the horses. One just has to rethink and plan a little different than when you are going backpacking. Lightweight and multipurpose things to bring is the clue to go horse camping with one horse.
Have you made a pack list?
Horse camping is great fun either with good company or by yourself. I too do all the dreaming during the wintertime and go to the mountains with my horses in the summer. The snow doesn't leave the mountains here before mid June. But I am never happier at any time in my life than when I go for a trip with the horses.