Been using dremel shimano shifters cables for centuries just because nobody carries shimano around here, and when you mention campagnolo the guys just go white as paper and start doing faces and heart attack movements
You can do the trick in the brakes levers if you want thats not a problem as long as it works, in the derailleurs you have to file or dremel and the difference is so minimal that it wont affect the design of the cable head at all. Is less than a millimeter and using a round stone thing i a dremel takes you maybe a minute to get it ready? maybe less if you know what are you doing?
About not using tools, well... in a tour in a bike that was decently set cables would last a long time, heard nightmares about shimano users with cables snapping at the heads after 6 months. In campagnolo personally never had a single problem neither heard or read of campagnolo users with cables snapping so don't see why a problem replacing cables in the middle of a tour, that could just darn bad luck, I dont race no more and even back in the day never saw cables snapping at the heads in 1 or 2 weeks tours, IMO you have to have just too bad luck to have a problem like that.
No tools? easy, take with you a swiss pocket knife thing that has a file, like in 10 mins that thing will be ready to go. Second option if you have support in a car, just take a couple of cables already filed in the car, would be just too bad of a luck to snap two sets in a month for example.
Good luck