So now it's actually in the news:
http://www.msnbc.msn.com/id/29638951/ A lot of objections were raised, and naturally the funding was one of them. But some other interesting scenarios came up, like if Congress was devastated by "a terrorist attack". Never mind that such a thing has never happened, and if it did we'd have bigger problems than some state losing its precious representation. But regardless of the reason for a Senator (or a bunch of them at once) to have vacated office, these are still things to thing about.
The VERY bottom of the article mentions a decent compromise -- a successor can be appointed, but must run in a special election within 30 days.
~Sean