Something like that could be easily built on top of the HSC, yes.
A better example would be UniSwap decentralized exchange as I think Bittrex is centralized.

The whole side chain will be programmable, that is where the appeal to me personally is, being able to build stuff that other chains have that we couldn't before due to not supporting secure decentralized computing and ledgers.

It'll change everything around here and to a greater extent the crypto ecosystem as a whole.. Anyone will be able to interface with HIVE given they've chosen to build out their own chains in a format that is supported by HSC then to HIVE.