I think the key phrase here is "patch together"... Why would you go through that pain to end up with a Heath Robinson solution that is unlikely to scale. Most serious PPM customers need something that can scale whist meeting all the functionality that Project Online currenlty offers. Out if 120 customers that have tried to make Project Planner work, every single one of them abandoned it as not fit for purpose. This is due to the deep limitations imposed by the platform. The interface is modern but still clunky, and the speed of updates is visibly slow, especially with large amounts of data. In a collaborative environment this makes the tool ineffective. No proper resource management, cost management, enterprise custom fields, deep task level dependencies and three tiered calendering are just some of the things that are not present and require significan time to develop. Lets face it, if it was that straightforward Microsoft would have done it already. Much better to go for a 3rd party full fledged replacement to Project Online than to try and cobble together something that will never reach the same level of parity. Most of our customers agree. The retirement of Project Online withour any direct compatible replacemen means Microsoft is sure to be exiting the PPM sector.