@gohan6425 There are several issues here which haven't even been mentioned. First, and foremost from a question of profitability, is whether it would actually increase sales of the manga. Kodansha has no interest in the growth or marketability of the anime series as they simply provide source material to the production committee in return for the advertising that raises. In order for them to be able to see it as a worthwhile endeavor, it would have to increase the sales of their manga in North America in excess of the cost of licensing and production of the single OVA. Otherwise, it is still a loss. Assuming that it cost ten thousand dollars to license and produce the anime (including all expenses down to printing the disks) which is a lowball figure, they would have to see an increase of at least that many manga at a price mark about five dollars higher per copy to include the disk because of markup of the book distributors and vendors in order to even claim to have broken even on the project. Anything less is a loss on the project.
Then comes the question of regional licensing. Because of the recent changes, Sony/Funimation/Crunchyroll (in some unknown mix of the three) hold the licensing for North America for the series. Because they essentially own the rights to all marketing of the series in the region, there has to be a legal agreement as to what materials are allowed. No different than the production committees in Japan have to agree to anything done by a license holder, the same would have to be done in any already licensed region. Money would definitely be involved, and further increase the cost of production. Sony/Funimation may not be able to control what work the voice actors are taking because of being non-union, but they could easily restrict the type of product allowed to be marketed within their region. I'm not bad-mouthing Funimation, but this is business, and money is always going to be the driving factor of any well operated business.