The Senate is undemocratic at it's foundation. The idea of the states themselves being represented in the Federal Government and not the "people of" the states being represented is an antiquated, outdated model going back to fiefdom and feudalism.
The entire system needs to be revamped from the ground up. Having a smaller body of the legislature (fewer members) is a good thing for things like confirmations and as a check on an over zealous House...but the Senators should not be representing such enormously different groups of people (Wyoming having the same number of Senators as California is a travesty for example).
Right. The Senate could work with no changes to membership rules if it was primarily advisory, i.e., it had powers roughly equivalent to those given to the Canadian Senate or the British House of Lords. In that case, it could also probably go back to being an appointed body. As it is, where it is as powerful or more powerful than the House in almost all ways, it would need to be thrown out entirely to be fair.
One should remember that the Senate was never intended to be a democratic body. It was intended to be representative of the sovereign states, much as the Council of the EU is represents the member states and acts in parallel with the Parliament of the EU to pass legislation. In that sense it's no more outdated than the EU.
If one looks at the EU as a model, then making the Senate a democratic or appointed body doesn't capture the need to represent sovereign states. Instead one could require more sophisticated rules for the Senate to pass or block legislation. For example, the Council requires 55% of the governments and 65% of the population to pass legislation from the Parliament. That's not dissimilar from the 60% cloture rule for legislation in the Senate, so it wouldn't take that much change to correct for population as the EU does.
