Nine Supreme Court Justices is not enough. They don't take enough cases, and in the ones they do take they seem to phone in their decisions at times. Nine Justices means that every selection of a new Justice is so fraught with significance that the demented old farts are reluctant to retire unless a president of their own party is in office. Also, it means that presidents feel obliged to appoint youngish Jusitices so as to have a lasting presence of ideological fellows on the Court when these guys aren't really ready. If you're under 60, you're not experienced or wise enough to be a Supreme Court Justice.
Having only nine means that you are likley to get less of a range of viewpoints than you might have if there were more Justices. Nowadays, the Justices are starkly right wing authoritarian versus starkly left wing authoritarian with no room for nonauthoritarian ideas.
Let's solve these problems by increasing the number of Justices to 27 immediately, Routine individual cases could be decided by panels of nine, chosen randomly from the 27 for each case, and cases of major Constitutional import could be referred to the whole Court. Also, I would require every Justice who has not previously served as a trial judge to preside over trials as an acting District Judge until they have a few trials under their belts. These guys are way out of touch with the realities of trial work and the nature of real evidence.
And the Senate and President would do well to consider picking Justices who have had real private sector jobs at some point in their lives. No prosecutor cum law professor cum appellate judge, please. How about an honest to God trial lawyer?
While we're at, let's increase the size of the House of Representatives to 3000. That would be one Congresscritter for about every 100,000 Americans. Wouldn't that be way more representative? And the range of views and ideas would be broadened. There'd be more districts, and I bet it would be harder to gerrymander them into rotten boroughs. Parties would find it harder to impose discipline, so individual Congresscritters could more often vote their consciences.
Finally, let's make the presidency more of a ceremonial post rather than an actual executive with power and adopt a Parliamentary system for the real work of government. The presidency has been a failure as an institution.