That's a pretty cool cover band setlist!
First thing I'd do is get some locking tuners on there.. I went Sperzel crazy with a couple of my guitars, and tuning is rock solid. They might add weight, but SG's are already poorly balanced guitars.
How bout some TonePros locking studs for the stopbar tailpiece? I wager that'll increase your sustain.
And of course (puts on broken record..) I love roller bridges. I never broke a string again (at the saddles) after putting those on my Les Paul. Those little 'V's' can be like scissors if you are an aggressive picker..
GFS sells pretty nice knockoffs of all these things, assuming they're not currently messing up orders.. a handful of people were having issues recently..
ps- I just picked up one of these roller bridges for my Epi Supernova, and it's my favorite roller bridge now.. super comfortable for palm-muting, and it locks
to the posts. It looked ugly close-up on the website, but it's very understated once on the guitar. http://store.guitarfetish.com/Wilkinson-Brass-Roller-Bridge-Locking-Studs-Chrome_p_866.html