Zion winter wallin'

Hello fellow MP'ers
I am making loose plans around new years and on to make a trip to zion/RR/the valley and so forth, and i have some questions about zion
If i am to do an older aid route, or one less travelled, what is considered appropriate behavior for replacing bad bolts/rivets/drilled angles/blown 'enhanced' hook placements?
What kind of bolts (3/8 or 1/2"? Wedge or 5 piece? Glue ins? How long? obviously stainless or titanium) is it ok to up rivet size to 5/16 or 3/8? If its a shitty drilled angle hole, do you patch and just place a bolt? If its a blown out bathook hole is a bolt ok, or would you rather a rivet? (Or another bathook hole, haha no way). What materials do you guys use for patching old holes?
Im looking to do a fair amount of solo wall stuff (desert shield, tales of the scorpion, etc) are there any other tips and tricks ya'll may have? I am very comfortable on granite. The only sandstone aidroute ive done was prodigal son (solo in a about 8 hrs) and am keen on any random tricks you zion wallrats have found handy (kinds of sawed offs to bring, bailing wire for rurp eyeholes,that kinda stuff)
Also if yer looking for free/aid adventures around that time of year im psyched to get on some routes with whoever. I just travel alone alot and plan on aid/ ropesoloing stuff unless i find partners.

bump...

Step away from the bolt kit buckaroo...

ok fellas i will definitely heed the advice
i don't plan on "swiss cheesing" anything, just wondering what one should do if old hardware pulls on me, no sense putting another time bomb in its place, (will ask Ron)
thanks for the civilized responses, i'd gotten so used to seeing people ripped to shreds in the forums i was prepared for the worst!

Yes, the responses were quite civilized, I'm impressed. Thanks.