While I do intend to also put some empty tubes with string in it inside the walls, your solution is not very handy for the entire house. Nowadays all the wiring comes pre-fitted into so-called 'pre-flex' tubing. This is flexible, ribbed tubing which usually comes on a reel. (see here for a photo). This is a very good solution for installing (saves a lot of time), but this is very bad if you ever need to replace the cables inside the tubes. The tubes themselves are just too flexible for that, and it also doesn't help that they're ribbed...

So good suggestion, but simply not do-able. Thanks for your thought though...