Run electrical wire outside in for new lightings for cathedral ceiling
I think your plan is based on a reasonable assumption - that when you drill in from the outside, you'll have an unobstructed path between the rafters to fish your wires up through.  

I'd want to verify that is the case before committing to this plan.  I'd want to drill holes in from the outside and be as sure as possible I could get a fiberglass fish stick up to the spot where the can lights are going before I cut holes in that ceiling.  This isn't a guarantee things will go easily but it ought to help.  

You are probably aware of this, but even with two very proficient people working, getting in place on ladders, scaffolds or etc. and fishing wires from the eaves to the ceiling is going to be challenging to do safely.  

I don't know if you'll be happy with the appearance of exposed outdoor cable under the eaves, if not, installing conduit up there will be  another challenge.  

I don't know if that ceiling is tongue and groove, but choose your hardware carefully - some may be much much easier to install than others.  

Wiremold is starting to look pretty good to me...