That is a very worthy idea. At one point the New Hampshire State Legislature was the third largest legislative body in the English-speaking world, after Commons and Congress. In those years NH had the no state income or sales taxes, and some of the lowest taxes in the country. I don't know what the situation there is now, but reducing the size of the Legislature made representatives more distant from the represented. Professional politicians took over and they were less accountable to the people.
Also, increasing the size of the House would probably reduce the role of television and big contributors, since it would be hard, at least for a time, to find the television time and money for such campaigns were the number of seats to be expanded. And if you increase the size of the House, Congressmen's perks would inevitably go down, at least for a time, and the citizen-legislators would want shorter sessions.
The downside is that some of the new legislators, with fewer perks, might be tempted to make the most of their benefits under the table. And salaries and perks would inevitably start creeping back upwards. But on the whole, you're idea bears much looking into. A larger house might provide some of the advantages of term limits without the drawbacks.
As for repealing the 17th, I don't know if it would have the benefits people claim for it. Legitimacy today comes from the direct mandate of the voters. Any unelected or indirectly elected legislature loses power and becomes peripheral.
So there's a trade-off involved. You might like the composition of an indirectly elected Senate, but the House would more and more shove it aside into a purely advisory capacity. I wish it weren't the case, but it just seems like human nature. Given the way people think about things now, those who can claim a full mandate of "the people" are in a position to marginalize those who can't.
It would also make it much more difficult for "house leaders" to whip representatives into towing the party line.
I think the other link that was broken was the tie between the voter and the Senator that goes THROUGH the statehouse. If you don't like the way your Senator is behaving (perhaps because he's bought by special interests, or the statehouse is bought by special interests and is appointing likewise bought Senators), then you vote out your state legislatures. Sure, this may take a little time to trickle up, but that was the intended process.
Of course, this was all thought up by 18th century people who studied ancient philosphy in the original Greek and home-schooled their children in Latin and calculus by candlelight.
-PJ