A constitutional amendment would be required to repeal the 17th.
The language of that amendment would need to include
the methodology which would replace the current system.
I would favor some kind of a system that encouraged the citizens of a state
to focus their efforts on issues within their own state.
Maybe something like providing authority for the governor’s
of the states to directly appointment U. S. Senators;
paired with them having full recall authority of their Senators.
I've seen a couple of ideas that are intended to help resolve deadlock in the state legislatures.
One idea would be to have the state Senate and House meet as one body to cast a vote, in case the two houses deadlocked on picking somebody.
The other idea would simply be to have one Senator picked by each legislative house, thus sidestepping the issue of deadlock entirely, provided one house doesn't deadlock internally.