You could post it at
http://hub.qgis.org/projects/quantum-gis/issues
as a feature request. But, as copied from an excellent blog post;
...4.
Ask a developer to make the changes for you. This is not terribly
effective – you’re basically asking someone to work for free, and take
time away from their family/job/hobbies/social life to do work for
you. That said, it does sometimes happen, and here’s a few reasons I
can think of why:
You’ve build up enough “karma” within the project through other
contributions. If someone has been heavily involved in the
non-development side of the project (eg translations, documentation,
helping users out on mailing lists/stackexchange, organising hackfests
or user groups, etc) then developers are much more likely to want to
help them out in turn.
You’ve got a fantastic idea which has just never occurred to anyone
before. By bringing it to the attention of a developer you might
trigger the “wow, I could really benefit from that too!” impulse which
is hard-wired into some of us!
It’s a particularly interesting or challenging problem, and sometimes
developers just like to extend themselves.
...
it's more likely you will get it done (for you) when you hire a developer to do this.
source: http://nyalldawson.net/2016/08/how-to-effectively-get-things-changed-in-qgis/