Has there been any thought to incorporating PSR-7 compatibility? Perhaps even as a configurable option.
For example, if the option is enabled, the callback for the routes changes from function(\Base $f3, array $args) to function(Request, Response, $f3, $args) or similar?
in such a case, the output is controlled by response rather than directly echo'd, etc.
I'd be willing to work on something like that.
-Rich