This is the approach we have been taking at CircuitBee (http://www.circuitbee.com http://www.circuitbee.com). We have Eagle and KiCAD importing, with versioning

This is the approach we have been taking at CircuitBee (http://www.circuitbee.com http://www.circuitbee.com). We have Eagle and KiCAD importing, with versioning on the way already. We're not aiming to replace the tools you already use, just make it easier to share your work on the web. I do love the idea of a web based EDA tool, but I'm yet to believe it can be done with performance characteristics that will work for any reasonably complex circuit.