OK I get that, in concept at least. To the extent that the legacy apps you are trying to migrate are based on some reusable framework that can be pulled out and delivered as a new type of PaaS container. Though if this framework is just a “black box” from the Cloud provider point of view then you are not going to get all that many benefits in this approach compared to traditional IaaS approach of bundling the framework w/ the app.

For example, Google did a fair amount of work on their Java and Python runtimes to offer them as PaaS containers that exhibit great operational characteristics. If you asked them to offer the same thing for Cold Fusion or ASP.Net, they’d have to do serious engineering in these runtimes too. Otherwise they won’t be able to provide nearly the same scalability/resilience and low cost of operation for these platforms that they do w/ Python and Java.

There is no silver bullet, but I can see how what you describe could be a new cost/benefit trade-off point on the axis from backward-compatible to forward-compatible. Though I am still unclear on the specifics and whether it all adds up in practice. Interested in any info/pointer you can share on this.