If you needed an inch or so you might be able to trim housings a bit. But you're over thinking this. If you bought an 80" or 2000mm inner wire and came up short you need a longer one. What is, is. It's not a problem to solve, just buy wires long enough for the job.
BTW- the 2000mm "standard" wire length goes back a number of years, predating Campy Ergo, to when Shimano STI wires took the shorter route out the side of the lever. It's fine for older road bikes, and mtn bikes, but apparently can come up short with the current under the tape routing on road bikes. It's possible that Campy and Sram added a few inches to the cables they provide in their kits, but it's hasn't trickled out to the aftermarket stuff yet.
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