These civs have been proposed before and so have many others, that's the easy part, in fact a lot of people want to see their region/ancestry represented. It's up to someone putting in the work to research and design them, and most importantly take the lead and follow through with the project long-term I guess what I can add from an 'inside' perspective: we're not looking for new civs to implement, it will be more than enough work to finish what we have already (some have been of the opinion we have too many civs - when I joined the project, we were only planning 6 civs for part 1! Former designer/lead decided to bump that number over time, but we're not in the position to continue that trend now)
Adding a civ is definitely a lot of work, not like a week long project but months/years. That shouldn't dissuade anyone but rather challenge them if it's something they want, but it does need a leader. Check out all the work that went into making the Mauryan crowd-sourced civ a success.
One thing is the topics seem to be forgotten, maybe someone should organize proposed civs with links to the topics, for reference and to prevent them being forgotten if they aren't bumped for a few weeks?