Honestly my problem is that all my designs turn into devboards since I always have a kind of "FOMO" of not breaking something out and then needing it later to bodge things... and then I'm left with a crowded board where I don't even use two thirds of things...

I‘m sure you've already considered that, but what about iterating your design, e.g. redesigning the board if you need more outputs?

Test pads are great for these anxious breakouts. I usually drop tons and tons of test pads on the back of my boards as it's a very dense and unobtrusive way to expose traces that you probably don't need.