You can still get around the 7 bracketed exposures. Not sure what the big deal about doing that is - quite simple. Put the unit in 7 bracket mode as mentioned above. Go to Exposure Comp./AEB setting and choose how you want the 7 laid out. Ex. all in 2/3 EC stops starting from 0 backward (Move M-Fn wheel until the layout is as you want it - in this case -4 would be the last one and 0 the first). Make sure camera is on tripod with release cable (best). Take the 7 shots. Go back and move the M-fn wheel so that +4 is the last one with the same 2/3 EC spread. Follow same procedure. Boom - done. Now you have 14 bracketed shots with two overlapped on 0. Simple.
That's great, but it's not only about the number of images, it's about the total dynamic range you can capture. From what you describe, you're getting a +/- 4 EV range. It should be possible to get, for example, a +/- 10 EV range. It doesn't have to meter to -10 EV; it just has to meter the scene normally and subtract 10 stops and increment from there.
Honestly, since you can do this exact procedure by hand, I think the simple (and obvious) solution is to get a solid tripod (which you should already have for landscapes), meter the scene and then slide the shutter speed as far down as possible and start manual shooting with faster shutter speeds. That's all they would have to do in firmware, so it's confusing why they always choose to limit AEB to +/- 3 or 4 EV.