It's a long time since fiat currency was pegged to gold. The only guarantee you have with fiat currency is that its vale will depreciate, and you will lose it if banks or governments get into trouble.
That is true, but the principle of the gold standard is still as valid as ever before.
If you have an altcoin that is being backed up by the amount of x bitcoin, it would naturally have the same value as that amount of bitcoin. I still don't see how it's not possible? An automatic "bank-exchange" that stores a reserve of bitcoin and an altcoin wallet that have the function of redeeming your altcoins for bitcoin.
The only thing I see stopping it is trust of the altcoin being able to manipulate the reserves of bitcoin. Surely it can't be impossible to code a contract that states that there can only be x alts for every btc, or vice versa? What have I missed?