XBT (Guess we are stuck with it)
Only if we want to conform to a standard that was not designed for cryptocurrencies nor with cryptocurrencies in mind (because they didn't exist).
The X is applied to everything
Guess LTC would be
XLT
Powercoin
XPT
Namecoin
XNC
SexCoin
XXX (Xsc)

Stuck with the X lol
XBT does not indicate anything about "non-standard". In fact, it is the opposite, it indicates following the established international standards. XAU is gold, XAG is silver, those are not non-standard currencies, they are just currencies that were not issued by any national government. Likewise, bitcoin was not issued by a national government, so its code should start with X.
Are you saying gold and silver are less significant than government fiat? X means non-government, therefore universal. Therefore, these should be regarded as more significant.
In normal usage, like where you would use $, BTC is fine. For places like exchanges where USD would be used, the term XBT should be used to conform with accepted standards.
In normal usage, like where you would use $, BTC is fine. For places like exchanges where USD would be used, the term XBT should be used to conform with accepted standards.