One major annoyance I've ran into when doing large scale building is when edges or previous construction interfere with blueprints and you have to manually place things, or ignore large areas and be very inefficient. This is especially true since you can't manipulate water right now without mods, there's no way to make a nice square section of land where everything fits if you play on a map with a lot of water.
My suggestion would be the ability to force-place the parts of a blueprint that fit, ignoring the rest. This would allow you to build tightly around water, around Roboports, powerlines and whatever else might be in the way.
Simply hold Shift (or Ctrl) when placing the blueprint and it will be force-placed.
I suppose it might be a bit too powerful, make base-building too easy? I don't know, I don't really think so. I think it'd be a fine addition, removing some irritating tedium.
![Image](https://forums.factorio.com/images/ext/b289d648974c803feb9d3d8a95a97c56.png)