An alternative to a pano head is to rotate the ballhead so the camera is vertical. If you watch the lens as it pans, you will notice that even though it follows an arc, the actual change in the frame-to-frame rotational center is not that big, and there is relatively little side to side parallax. I have gotten some very low stitching errors working that way in cases where I didn't want to carry the full pano head.
I have a few TS lenses, and I have to say that in almost every case where I don't have to shoot fast I prefer using focus stacking with Helicon Focus. TS lenses have problems when nearby objects are randomly distributed at different heights which may fall out of the best possible TS solution, but which in every case can be easily handled with Helicon. Tree branches at the top of a scene with nearby objects on the ground come to mind. Helicon presents slight difficulties where you can get a fuzzy halo when a very close object is superimposed over a very distant one, but there are various ways to fix that quite well.
Looking at your kit, I would add an 85mm prime. I personally use 28, 35, 50, 55, 85, 105, 135 a lot, and a 200 maybe twice a year. BTW, the old 55mm, f2.8 Micro Nikkors are quite possibly the sharpest and most immaculate lenses in the known Universe. I've been using those (mostly) old Nikkors on the 5DII and the results are wonderful although I must say I have gotten really good at guessing exposure! Yes I think you might gain something with the extra megapixels. I routinely push the focus-stacked, single row 5DII images to 30" high with nose-on-the-canvas quality, which I wasn't quite getting with the older 12mp cameras.
PS, I also had my photographic career interfered with my a 25 year long day job. Was glad to reclaim my true mantra, hope you are enjoying your return to the true fold.