Possible?
Certainly possible, but don't expect it to become part of the standard MantisBT in near future.

You can write a plugin if you need it in short term.

Submitting a patch is always a good idea, as it increases the chances of improvement eventually making it into MantisBT core. All contributions are welcome and greatly appreciated.

Patch submissions can be made in several ways. In the order of preference:

1. Send us a Pull Request on our Github repository [1]
2. Attach a GIT patch to the issue
3. Attach a Unified Diff, clearly specifying the patch's base release

Kindly avoid to upload entire modified PHP files.

Please make sure that your submissions adhere to our Coding Guidelines [2], if they don't your patch might be rejected.

[1] https://github.com/mantisbt/mantisbt
[2] http://www.mantisbt.org/wiki/doku.php/mantisbt:coding_guidelines