Senate term lenght

[minionofmidas]

It should be vaguely proportional. Not necessarily exactly so, but the current state of affairs is ridiculous and a serious problem. Then keep its electoral arrangements roughly as they are (fairly lengthy term, partial renewal, details are unimportant), lengthen the House term by a year or two, and make the President elected by the House. Ie, ensure he (at least usually) always has the support of the Lower House, but create no such linkage for the Upper House. Make the Upper House marginally less powerful than the Lower (full equality exists in Italy, and sort of in the US, where the Senate is arguably more powerful, net speaking), but also not a complete joke as in some countries that might just as well abolish it.
That seems to be what works best. Just saying. No, actually it'd be preferrable to have that President be a Prime Minister and have some more-or-less elected, purely or near-purely figurehead President. But ensure he doesn't cost too ridiculously much.

[minionofmidas]

Oh, and it should be elected by the state legislatures again.

I have never understood why anybody wants this.

The idea was that the Senate would be a body that acted to preserve the power of the States and help keep the Federal government weak. 

It has never worked that way, though. The way to do that would be to give the federal government (all branches) very few powers. And make the Senators directly dependent on continued support of their state governments. And, most crucially of all, to not have any states too small to fill their then-larger shoes in the first place.