Bottom bracket damage work-around I built up a Specialized Rockhopper over this last summer, ending up with a sleek, blacked out, Deore &amp; XT equipped thing of beauty.  During a brief stop at a buddy's place, the 12mm Kryptonite cable lock was forced and it was gone.  About five days later, I'd chased it down, finding it completely stripped.  Even the BB cable guide was removed.  

I've decided to rebuild, mostly in hope of transforming my anger as much as the Specialized.  The left bottom bracket shell has some damage that concerns me, I'm asking for possible solutions and to run by ya'll my thought on a possible fix. 

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I'm going to face this left side, if only to remove the galled aluminum that sticks out past the original, proper edge.  Could one be more aggressive and remove 2.5 mm from the shell width on this left side (ending up with a 65.5 mm shell) then add a 2.5 mm spacer to bring the cup out to the 68 mm position?

Can I use that many spacers with outboard bearing cups? (There'd be 2, 2.5 mm spacers on both the right and left side).  I remember on cartridge bearing BB's that there is a limit to the amount of spacing tolerated and it's different for metal cups than if plastic.  Is there a similar restriction with outboard bearing cups?

Finally, is the frame ruined? (If so, somebody cue AC/DC's "Dirty Deeds" cuz it's gonna be my jam for a while).
You could most likely also instead do the following: face the frame by 2.5mm... don't install a spacer under either cup.. install them directly into the frame. When installing the left side crank slide a spacer (1 1/8 inch headset spacer for example with on side pressing against left side crank and other side pressing against the rotating ring on the bearing cup) over the axle of the crankset before proceeding to install the left side crank arm. Make sure to choose a spacer with just enough thickness to ensure you can adjust it so there is no play on the bearings/crankset axle. I've done this on one of my mountainbikes and ridden it for well over two year without issue.
Using this method you have the entire bearing cup's thread length engaged in the frame even after facing off 2.5mm (or another amount for that matter).

Your suggestion of facing off only the called aluminium sounds like a good option to me. I believe the amount/total thickness of spacers underneath the bearing cups is limited because there needs to be a certain length of thread engaged to aquire the required strength. This would also explain why it differs between metal and plastic cups (since the latter have much stronger threads). This being said a 2.5mm spacer shouldn't cause any issues based on my experience. Perhaps you could consider tightening the bb cup on the faced side a little less (make sure it's properly snug though otherwise you'll ruin your threads most likely ... As is also the case when not tightening a pedal correctly and using the bike after) and installing (high strength?) Loctite or another thread locker to prevent the cup from loosening. .