I hate to be the bearer of bad news, but this feature request has been declined.
SO microsoft decided that teams needed a chat room and file repo. These can not be even be hidden or moved. So there are not tabs but system requirements. Which would mean that if you ar enot using chat and file repo as a main use as a team tehn youa re not using the product as it was intended. Any other tabs are thus meant to be optional or something. This is confirmed by the fact that you can not even export the wiki pages to a word document. It's a real shame really. If those tabs are required by the system then one work around could be the possibility to hide them or move them. Easy enough I would say. But there must be some grand design somewhere..