1 satoshi = smallest unit, pretty much in general use today
1 bit = 100 satoshi, eventually every day use, coffee, sandwiches, etc.
1 XBT = 1 bit, should be the official symbol on all exchanges, forex, etc.
1 BTC = 1000000 bits = kept for dealing with larger amounts, may fade
That is crazy. Adding more terms doesn't make it simple. Just stick and "XBT" is a totally different term again.
kBTC = 1000 BTC
BTC
mBTC = .001 BTC
uBTC = .000001 BTC
Now that is easy and simple and follows SI standards. It can also easily extended in either direction. One term and stardard prefixes.
I totally understand where you are coming from. The XBT thing is important because it would/will be the standard symbol for Bitcoin in the forex markets. X = not from a specific country like XAG for silver and XAU for gold and "BT" for an obvious choice for BiTcoin (could also be XBC probably). "BTC" does not follow the standardized naming conventions, it was just made up out of thin air a long time ago - here in these forums actually.