This is a great article, Sophie; you pretty much took the words out of my mouth! I’d written a response to another article in support of wireframing, and yours is a great companion piece full of practical advice.
The one concern I have with any kind of tooling during ideation or quick iteration is that designers tend to get stuck in and go for ‘perfect’ before the ideas have resolved themselves. As you say, the wires are there to convey function and purpose, nothing more. Lined up grids, perfectly balanced margins, and anything more than square corners just aren’t needed.
I’m currently using Sketch to digitise my wireframes – outside of that it’s whiteboards, pens, and paper for the whole process! – but do quite like the look of something like Balsamiq to remove myself from the visual temptation. Have you ever used Axure?
I hope you don’t mind me sharing this article with my team!