I wouldn't use that list as the be-all-and-end-all, afterall it doesn't take into account sidewall height. A higher profile tyre is much easier to stretch onto a wider rim than a lower profile one. Sure, there is no real chance of putting a 185/40 tyre on a 7" rim, but a 185/65 can be stretched a fair bit more (more sidewall, you see). Heavier cars need wider tyres because they squash more, so if you stretch a narrow rim on you'll end up cornering on the sidewalls. A MA61 Supra is about 50% heavier than a KE55.
As to having different width rims front and back, most people want to have matching wheels all-round, and most factory wheels (apart from supercars) are the same size all-round. Thus, if you want matching style rims, you probably need matching widths front to rear. And what about the spare? Do you carry a front or a rear, since you're not legally supposed to have different sized tyres on the same axle (unless it's a space-saver)