How flexible is the Counterparty Protocol in terms of it being run atop other alt-coins instead of just Bitcoin?
Has anyone got any opinions about which alt-coin might be the optimal base for Counterparty?
Most alt-coins are nearly identical to Bitcoin, and Counterparty will run fine on any one that is. It would need a little tweaking for something like Namecoin or Peercoin, but not much, I think.
By which you mean support for OP_RETURN feature of Bitcoin? I think I read something on that before, i.e. that it is used to store data on the XCP transaction taking place.
I was reading an article on one of the bitcoin magzine websites and they mention that apart from the obvious external dependency (i.e. btc blockchain) the other problem is that it could be sluggish or time consuming searching the block chain for specific transactions that have stored XCP data. Is this a concern for you at this stage.