I agree that this should work fine and will actually be a lot of fun for you. I rode H/J for years and there was, of course, always an instructor in the ring-- I wouldn't have felt confident without one plus how do you move the jumps up and all that without one?
With dressage you can be more independent and feel like you are really doing the training yourself with the aide of the lessons. I love it-- my instructor has started saying "You ride your own program while I watch and give you tips" which means I have to do the thinking and know what I'm trying to accomplish in my session with the horse (of course, she'll step in if I get off-base).
It feels like I'm in control and I'm even kind of a horse trainer vs. just a client of a trainer. I loved jumping but I love dressage even more, partly because of the sense of independence. Enjoy!