what if that item becomes naturally cheaper? more costly?
what if we pin it to bread, but then some scientific breakthrough reduces the cost of growing wheat and turning it into bread by 2/3rds? now our dollar's worth collapses as well.
Pinning it to something that is less volatile - like the supply of gold - is also a non starter, because there's not enough gold, and as production increases and gold does not, you get strong deflation.
I would reduce the Feds' mandate to just holding down inflation, and subject it to more congressional oversight.