Scaling in baking can be done just fine in most circumstances. Bo Friberg, in the Professional Pastry Chef, states that all of his recipes (most of them scaled for professional use) can be multiplied or divided 4 times. If you want double the recipe, then just multiply every ingredient by 2. It isn't rocket science...
As for using baker's percentages, I think you're just complicating your life for no reason. A Baker's percentage is simply the ratio of a given ingredient to the amount of flour in the recipe. If there's 5 oz of butter and 10 oz of flour, then the baker's percentage for the butter is 50%. I am not a professional, so I am no expert on this, but my understanding of this system is that it is used primarily as a tool for comparing recipes to one another. If you want to glance at a brioche recipe and immediately understand how it compares to another brioche recipe, for example, a baker's percentage can be a useful tool. When I see a 50% butter figure, that tells me immediately what kind of brioche I'm dealing with, versus, say, a 100% figure. Using this method does not appear to have any real application to home baking. I imagine it helps streamline recipes for professionals, but honestly, I can't see why you'd bother at home. Just multiply and divide and you'll be fine in most cases.
That being said, it is true that you have to be careful. There have been times when I have gotten odd results when I tried to divide or multiply by 4 or more, although I have never had any trouble doubling or halving any recipe. I think there are two main reasons why excessive multiplying or dividing can ruin a recipe:
1. As others have alluded to, some ingredients, most notably yeast, do not necessarily scale well. There are also situations where there are physical and practical limitations to scaling: try to scale a cream the butter cookie recipe too far down, for example, and there isn't even enough butter for the mixer to mix; before you even start the machine, all the butter is dispersed on the side of the bowl.
2. Recipes are not perfect. The ingredient ratios are often approximations, especially when you're dealing with volume measurements, which are highly unreliable. Your 1/4 cup of flour may not be the same as someone else's. And this discrepency will only get bigger the more you scale the recipe. A recipe that more or less works as is can completely break if multiplied by 10.