Guys,
Nice work on Stratum. A note that I hope you will take to heart --- this problem is already solved by open protocol standards (at least in TCP point to point cases). The rest of the financial world is already using it so for the purpose of easing future integration, it's best to leverage that instead of re-invent the wheel.
The FIX (Financial Information Exchange) protocol already covers all the requirements listed in Stratums spec and has been used for over 15 years in the financial world for relaying messages for trading, market data, request for quotes, and others. A recent open source implementation in C++ allows you to easily define new schema (xml, json) to extend the protocol.
http://fix8.org/The protocol supports replay through sequence numbering, etc.
There are open source implementations in C++, Python, and Java, and possibly others. Oanda's FX trading system uses it:
http://fxtrade.oanda.com/images/FixSpecifications2.pdfWhat you want is this to be adapted to the web server/client model.