Ok, sounds reasonable to check it that way.
You should (but I guess you already have)
include the option to switch off the string pulling calculations
for performance issues in large levels.

I still go for pure node to node movement
to avoid situations, where the bot might get stuck on
corners and other obstacles. It looks more "on rails",
but the movement of the bot is smoothed by some other means to,
so he does not have a choppy movement.
(similar to watersking with a rubberband)

Realizing a nav-mesh would work out really cool in
a game, but of course the creation of such a mesh
would be very hard to realize by an automated script.
A very skilled level-mapper could do that by hand,
(but lots of work of course)