For what it's worth, that discussion was only about the reuse after authorization, not about the time between creating an order and checking the authorization. That time (at least as of that discussion) was 7 days, and I think there was recognition that that couldn't be reduced significantly due to wonky DNS setups like the one mentioned here.
But I'll second the recommendation for acme-dns. Or, maybe you could see if you could get away without needing wildcard certificates and thereby being able to use an easier challenge type. (Few people actually need a wildcard certificate, and just automatically getting separate certificates for each name can sometimes be easier even though it ends up with more certificates.)