OK, a few thoughts:
1. If these “judicial districts” can diverge in population by more than 10%, then the Democrats could redraw them when they get a big congressional majority at some point (and don’t point out how difficult that would be given our natural advantage in the House and Senate, since 2006 and 2008 occurred despite our natural advantage) and really screw us. If we need a system tthinking that we can exploit it, count on the RATs screwing us eventually.
2. I don’t like popular elections of judges, and having them at the federal level (even if only for SCOTUS) could be particularly pernicious, even if Justices are elected by voters in particular multi-state judicial districts.
3. Having Justices serve staggered 18-yea terms, with a seat up every two years (one per Congress) so that each presidential term would see two SCOTUS appointments (preferably one in the first year and one in the third year to limit the effects of election-year politics), would give the voters more of a say in the selection process, given that we wouldn’t go through 10+ years without a SCOTUS vacancy like we did from 1994 to 2005 (when the Senators elected by the voters in 1994, 1996 and 1998 didn’t get to vote on any SCOTUS appointments during their respective terms). While a president could make more than two appointments (subject to Senate confirmation, of course) during a term if a Justice dies or resigns, any appointment for a partial term would be valid not for 18 years, but only until the term expires, which greatly reduces the benefit of self-dealing by Justices that time their retirement to coincide with a president and Senate of their preference. And by substituting an 18-year term for the traditional lifetime appointment, it eliminates the incentive for presidents to appoint young and possibly unvetted judges to SCOTUS, and permits them to name 60- to 65-year-old judges with a proven track record, since both a 50-year-old and a 65-year-old would serve the same 18 years. So if I were to change the selection process for SCOTUS, I would go with staggered 18-year terms.
My idea of “term limiting” them would not only to have them up for retention, but ensure they couldn’t serve for life by setting a maximum number of years they could sit on the SCOTUS bench. I’d probably make it either 25 consecutive years or the age of 75, whichever came first. Thus, a President could appoint a 65 year old judge to SCOTUS if he wanted, but the justice would be ineligible to continue serving after a decade.