I see your point, but agree with R2D221 and Jon Matonis. Don't know whether 'catastrophic' is the right word, but it would create too much confusion.
As per your example, from the small/medium business or even customer's perspective, you'll be more likely dealing with amounts ranging say between BTC0.01 to BTC100 rather than BTC0.00014321. A few examples:
BTC99.15 = XBT99150000
BTC1.456 = XBT1456000
BTC0.025 = XBT25000
To me, that doesn't look much better than 0.00014321, does it?
Numbers larger than 999 are generally presented with commas for readability. There is no convention for digit separators for numbers less than zero. So your comparison should be
BTC99.15 = XBT 99,150,000
BTC1.456 = XBT 1,456,000
BTC0.025 = XBT 25,000
BTC0.00286 = XBT 286
Only the last two of these numbers is in the range of realistic daily transactions (e.g. song download or lunch), which are the transactions the display unit should be optimized for.