Interesting. However, I don't see how one satoshi can be a transaction with dust limit of 546 satoshis.
If each share will be represented by 546 satoshis, nasdaq will need 546x[2.1bil shares]=~1.1trillion satoshis daily=11 thou bitcoins daily (three times more than daily production).
If each transaction is represented by 546 satoshis, then 546X2.5 mil daily=~1.1 bil satoshis=100 bitcoins daily-more doable.
However, once these satoshis are associated with shares, they will not be able to be associated with newly traded shares, so a constant flow of satoshis will be directed toward shares and these will be removed from daily circulation (until those shares are traded), hence a pool of available satoshis will be constantly depleting.
You are also forgetting transaction fees. Especially when the transacted amount is so small, the fee will be required in order to ensure it gets included in a block. So you would have to add 0.0001 BTC per transaction on top of that (10,000 satoshis). Now those numbers get much, much bigger.
(ref:
https://en.bitcoin.it/wiki/Transaction_fees)
The fast majority of that daily volume are HFT algorithms holding onto securities for very brief periods of time. This type of use case does not need a colored coin solution. A colored coin solution is more appropriate for real investors who purchase and hold a security for some real period of time.
I could imagine the NASDAQ creating a 2 tier system, where there is an in-NASDAQ market for short lived HFT trading usage, and also a colored coin market where securities can be traded and withdrawn onto the block chain. Trading and withdrawing onto the block chain would be marginally more expensive, but would make sense for real investors buying and holding. The HFT volume would stay on the current system centralized since that would be cheaper and HFT does not need blockchain security.
I think if you took HFT type trades out of the transaction volume, you would now have something reasonable for a colored coin market.