Interseting conversation.
My first four years airline flying were done with no area nav capability or autopilot and I feel pretty comfortable that I could get by ok going back to basics if I was without my dual gps, irs , fmc combo, and one of the first mental calculations i do upon reaching the cruise is my kg's per nm and my nm per minute for todays conditions, but.........my first priority is providing the safest travel to destination for my passengers. In this situation utilizing the capabilities of ATC and keeping the workload of myself and my copilot as close to normal as possible would achieve this. If for reasons of fun/ego etc I decided to do revert to old practices when it was not the only option, I would be
a) creating more workload than was required of the situation
b) increasing the chances of missing something normal (a checklist or wx change or atc clearance or transition altitude etc etc)
c)reducing my situational awareness by diverting my brain cells into calcs rather than leaving them free to observe how the flight was progressing.
d) creating a 'non-normal' situation and in non normal situations errors are much more likely to occur (lets face it, navigating like this is, now days, not a normal situation)
In addition to these things, my first officer may be more rusty than me or completely incompetant in this type of navigation (thats the world we operate in,I'm not saying it's right) and so I am effectively making it single pilot as well, taking him/her out of the loop, reducing the chances of effective cross checking.
I have no doubt that I could do it safely, but it wouldn't be the safest option, and unless there are significant costs to the safest option, I'm going to take it. If I want to practice that sort of navigation there is nothing stoping me from doing so when the fmc's are working fine, that way, one day when it is the only option available to me I will be proficient, but to do it when other options are available in order to have fun or stroke my ego is , in my mind, irresponsible.
Just my 2 cents.
Framer