FWIW the rat's nest of wiring on the bike I mentioned earlier was worst around the handlebars. Again there is a conflict; keep it all accessible so that it can be fettled/repaired or hide it all so that it is less easily damaged (but more difficult to repair/maintain, obviously). There are always wires somewhere that get flexed/vibrated and even well specified ones can still fail. I think that you are doomed to have exposed wires somewhere and these can get snagged.
It's a balance, and each rider will find that balance in a different place. With typical bike packing setups where you have bags attached to the handlebars, this gets in the way of exposed wiring, having the wiring under the bar tape will also protect it.
But by having multiple shifters, be it the brake lever ones, climbing shifters, and then shifters on the tribars, if one fails, it's annoying, but not endex. Carry spare cables, and it should be possible to rejig things to make sure something works.
Re 'staying in one position'; I have never found this a really good scheme. Once every few minutes I stretch, change position, ride out of the saddle or similar anyway, just to keep good circulation in every part of my body. Changing gear is just another excuse to move around a bit, so I don't begrudge it. BTW I don't find STIs especially comfortable to use (maybe back to the wrist thing?) and in many ways prefer a standard gear lever mounted somewhere handy.
Yes, we all move around, but when you've just got comfy on the tri bars, and need to change gear, it becomes a pain, trust me, I've been running my current setup for 9123km so far this year. I am very closely acquainted with the quirks of the setup and what bugs me and what doesn't. Having to move off the tri bars to change gear is really annoying.
This is largely a matter of taste, each rider will do things different, each will find different things annoying. Cycling is a very broad church. There is no one right way.
As a general comment yes the big squishy bit is likely to be a main point of weakness, but to my mind this would only make me prioritise reliability and repairability over everything else when it comes to choosing equipment; you are going to feel doubly or even triply gutted if some equipment fault (that could maybe be easily fixed if you were in a well equipped bike shop) leaves you stranded in some remote location. As I mentioned earlier, looking at those riders on similar events who had equipment problems is worthwhile; their problems would have been some combination of bad luck and bad choices; telling which and making a rational choice isn't easy but there is more to be learned here than (say) what equipment a winning rider used. A winning rider would have got some marginal gain from some equipment choices but others using similar equipment may not have finished the event at all.
You have to look at the setups used through out the race. Not just what Ede uses, but also what those who DNF'd used, what those who came in after the time limit, those who came in with hours to spare.
This is why I cycled through the night to be in Geraardsbergen, to talk to riders, to look at what they are running, talk to them about their decision making process, to take photos of the setups, to get inspiration. I didn't race this year, but being in the start was what cemented my decision to apply for 2019. I made friends with a number of riders who raced this year, and am still in contact with them, it's been really enlightening as to what did and didn't work.
There's one rider who was using a triple on a square taper bottom bracket, and she managed to crack the inner ring of her triple. Had to get it fixed in Switzerland. Finding a bike shop with the right part was hard.
And that's another key point. Bike shops are very much variable in their quality. On my scandi adventure last month, I had to go to several bike shops over a 100km distance to find one that was a) open b) stocked 700c inner tubes. Yes you read that right. 700c inner tubes were not stocked by one of the bike shops I went to. They had tubes for upto 23mm tyres, and they had them for 35mm and bigger, but nothing in the middle.
I'm very much working on the assumption of being totally self sufficient mechanically.
J