I'd like to deploy regular war (not OSGi-ed) in Equinox' Jetty. Doable?
The OSGi Web Container specification (part of the OSGi Enterprise Spec) allows you to do exactly this. You will need an implementation of the spec, and there are two available I believe: in Eclipse Gemini or Apache Aries.
Note that deploying a plain WAR to OSGi generally means you don't get any of the advantages of OSGi such as the ability to modularise your web application into bundles. However it is a useful transitional step.