I'm getting towards the point in my Japanese journey where I think a having an option to do JP -> JP would be very beneficial for learning and was wondering if plans for such a thing exist at present, because I love renshuu and it's format and have been using it since the start of my Japanese learning around a year ago.
You should really ask this in about renshuu. Michael might not see your question here.
As far as I know, (and I don’t speak for Michael), there are two issues: data and time. For data, there was an attempt to get jp definitions from Wiktionary. I think that is on hold for now. For time, it’s a question of priorities. Right now, Michael is focused on other things. Maybe next year he’ll take another look at this.
Not that it's not a priority, just that there is no good data for it (yet). We looked into the wiktionary data, but it was far from what could work in renshuu without significant editing and checking.