I've talked about this subject in the past and made a feature request in a past suggestion page.
I also looked into it and tried to hack it into the engine, but from what I've seen it's pretty hard if not impossible to do with the way C3's rendering is done at the moment.
I agree it would be really useful if this became a thing.
Mikal and I both experimented with making pixel shaders that can repixelify a layer with linear sampling. That might be worth a try.