While I don't disagree having some utility aliases would be a good idea, the reason why MMD is deprecated is because we cannot be certain whether the person searching it wants to see MMD fanart or MMD posts. Someone who just writes in MMD would likely not even bother with adding
_(medium) at the end. And if that were the case in searching, it's probable it wouldn't be the case when someone is searching for the tags for tagging purposes. If the aliases do go through though, I wouldn't challenge it.