Absolutely agree with you there. The taper profile needs to converge on a theoretical zero width tip, which in practicality has to have some width, as you mentioned.
This means that the limbs, of tillered perfectly symmetrically, probably won't be exactly the same thickness throughout, but need to taper ever so slightly in the last 1/4 of the limb or so.
You are correct on needing to taper the outer limb thickness some if you straight taper to the nock width. You can keep the limbs constant thickness with a narrow lever to the nock, as shown here:
It is a bit hard to tell in the picture, but the end of the limb is parallel width for about the last 3.5" or so. It is 5/16" wide for that whole length. This lets the limb width taper follow the theoretical ideal that goes to a point at the nock, then transitions into a slightly stiff tip lever where the limb width goes below the 5/16" width. I added a tip wedge during layup to stiffen the tip a bit more and guarantee it was strong enough. This was the first time I had tried this and I was worried that the spindly narrow tip would be too fragile.
Mark