Just a quick comment (I’ll edit when I find the time):
The Problem is that j3o isnt really backwards compatible so while it could work with newer versions it could also lead to Problems (I Think I had it that 3.2 j3os had Empty Animations in 3.1).
I dont understand 100% where its lagging but we could only really fix 3.1/3.2 issues.
Another thing worth noting is that the blender importer got many improvements but is still really imperfect. You could also try xbuf which is superior, but it will also embed the Material. Also on your current state it might not be wise to change the asset pipeline.
But with blender importer you should be able to Click on “generate Material” to Export the Embedded Material so its like with ogre (if I understood the problem correctly).
For the lagging: is that for every Model? Also on other devices?