No, we have no plans to support those things.
For image conversion, the GD library is available. I’ve never had to do any image manipulation code myself, but I believe GD does image resizing as well.
I’m not sure why Imagick is disabled, but as far as I know the majority of shared hosting providers block it so there must be a good reason.
system() and other shell command functions will never be allowed. From both security perspective (shells scripts are not affected by PHP sandboxing) and performance perspective (it’s easy to have long running shell scripts and it’s harder to restrict that than with PHP), there are very problematic, especially on free hosting.
We don’t allow media uploading and sharing sites to be hosted here anyways, which is why we have no intention whatsoever to start supporting complex media transcoding libraries.