Replace indexed (Sora) shifters with friction??

I have no real knowledge or experiences of shifters pre-Rapid Fire/STI, but I think you can get indexed downtube shifters that can revert back to friction mode if something goes wrong with them.

I don't think there is going to be that much work mechanical-wise to move back to downtube shifters, I guess you might need a new brake lever if your current STI shifter is completely stuffed.

Actually someone at work has a bike with Ultegra downtube shifters, and he was saying that modern derailleurs designed for index shifting are more forgiving when used for friction-shifting, as they have a bit of play in them. Saves you from having to get it "just right" every time.

I know these arnt exactly downtube shifters, but have you considered bar-end shifters? Ive got some Dura-Ace bar end shifters on my new undelivered bike, and have the same shifters on my recumbent trike. They work well and have had no problems with them. The ones I have allow for indexed or friction mode selection on the fly which can really handly when the derailleurs are just not sitting right.

I cant find them on the Shimano website though..but here is a picture of them..http://www.coloradocyclist.com/common/products/productdisplay2.cfm?PRRFNBR=10977

They used to make Ultegra barends aswell, but I had alot of difficulty finding them so they may not be making them anymore.