WebSphere 8.5 is a full OSGi container supporting Blueprint just as Karaf does.
You can, in theory, run your camel bundles or whatnot just as fine in WAS8.5. However, Apache Karaf is a lot more aligned towards running ActiveMQ/CXF/Camel stuff than WebSphere will ever be. Installation in Karaf is a few commands, where installation and configuration struggle in WAS85 for the Camel feauters and basic camel routes is .. well, a headace when I tried it last time. Others seems to have the same struggle.
I have rather good experience of running Camel apps inside WebSphere Application Server, but that was by embedding Camel in a standard WebApp, not using the OSGi stuff. So, embedded web apps is my recommendation for running Camel inside WebSphere.
For the "replace AMQ/JMS with HTTP" part. You are aware of that you are replacing pears with apples, right? JMS has a lot of features HTTP does not have (and some overhead compared to HTTP). For the sake of completeness, WebSphere also has a JMS provider built in. So if you have a large HA secured WebSphere infrastructure, the WebSphere (SIBus) provider might be a good choice. Otherwise, ActiveMQ rocks :-)