I think if you can actually get a pitch clock/batting clock/robo strike zone working, that will have a big impact on keeping action moving. If you can actually shave 5-10 seconds off each pitch, that alone saves you about 30 minutes a game.
I could also get behind banning extreme shifts. Yeah, it ruins the true analytics, and stuff like that, but if balls in play are more useful, that might help encourage less guys to swing for the fences. I think robo umps could also help put more balls in play, since players should end up with a better idea of what's what, they should be able to better manage the strike zone, and the only pitchers who can make batters miss are the ones who can sequence and hide pitches properly so batters guess wrong.
As for 7 inning games making the record books obsolete,
@WeHaveMoreCupsThanYou, which records do you think will suddenly fall because of that? Do you think someone will hit more than the .471 that Tetelo Vargas hit in 1943? Or if you want to skip Negro Leagues records, the .440 that Hugh Duffy hit in 1894? Is there a pitcher who's going to beat Old Hoss' 60 wins in 1884? Or if you only care about modern records, yeah, true, with 7 inning games it's unlikely that anyone will catch Henderson's 132 steals in a season, but then again, was anyone really getting close to that? I mean, even with our insane current strikeout rates, no pitchers are even coming close to catching Nolan Ryan's 383 from 1973 because they simply don't pitch enough innings. The only important record that anyone even has a chance to beat is the HR crown, but modern HR trends just means everyone and their mother can hit 20+, not that the top guys are nearing the 70+ from the record.
I mean, yeah, it might mean that modern players will have much less chance at reaching 3000 hits or 500 HR or 300 wins, or some other career marks like that, but you know what? They already are for a number of other reasons. The change to 7 innings is a drastically smaller change than MLB has gone through in the past.