As far as pocketing off the part extending the geometry is the only way with the standard pocketing tool path I think a lot of CAM programs are like this. The dashed line with High Speed pocketing is a great feature but I agree a serious amount of code is generated.
For your slot I would create a center line in the position for the slot and run it of the job by the tool diameter on each side. Then I would turn that line into a Contour with the direction arrows running in the direction you want to slot.
Then use the profiling tool path in 2D milling with no offset for the slot.
I do a lot of milling that can be best described as facing with islands and normally use HS pocketing with all its code, but have just started looking at the side roughing feature in V24 as another way.