Well, touring is a bit more than playing 2 hours at night, there's still the traveling, the soundcheck, eventual press, finding something to do in the idle hours etc... at those levels it can still be fun but definitively it's no vacation with 2 hours of playing.
About a small club show, I think the logistics would be a nightmare. There are stadium shows that sell out in a dozen minutes, the server that would host the site where to purchase the tickets should be made of adamantium to hold all the accesses that people would do for a mere 1000 or 2000 slots. And then bringing the huge Metallica machine into a small club (ok, you strip down everything, but still)... I don't see it happening, glad to be proven wrong however.
I guess the gimmick where everything catches fire during Enter Sandman and then they have to play the encore on a reduced stage with just two lights like it was back in the day it's the most "small club feel" they'll ever get.