maybe I'm saying something stupid, but wouldn't it make more sense to move the revision enable/disable option to the 'admin/content/types/$type' in the first place?

if people disable it for a node type, it doesn't need to be displayed any more on "node/add/$type".

When it is enabled for the node-type, perhaps a checkbox to "Do not create a new revision" (with a access check for 'bypass revisions') makes sense?

It are just some thoughts, and perhaps not the right. But to me it makes more sense..

Stefan