My observations on the last item (4th tier) first.
1) I have mapped very much longer hiking routes in the one country with three tiers [national (1), regional (10) and local (so many I lost count)]
2) walkers to take 4 or 5 days to cover what a cyclist will do in 1 day.
This is a generalisation based on my experience.
3) my expectation is that most of the Erie Canalaway tier 4 are about right for a daily effort, some (especially after Syracuse) will be a stretch and some might be combines.  By Empire State Trails have made the selection and that is what I will keep to: it is their creation that we are trying to give effect to.
3) In this case the "problem" tier is having three distinct route groups 
4) So, can we consider NOT having that first level Empire State Trail super relation.  I suggest this as a talking point only.

My comments on you substantive points above are in the next post