And people are still misconstruing why/what Harmony Gold is suing Tatsunoko over. They are not suing over ownership or any IP rights of any sort. They are suing Tatsunoko saying that Tatsunoko hasn't paid them some money they were owed as per the Arbitration Agreement.
Also the Arbitration Agreement even with the 2003 Amendment does not actually spell out anything that actually weakens Harmony Gold's case, at least in the publicly verifiable sections released so far. It certainly casts some interesting implications but doesn't actually spell out that Harmony Gold doesn't have the distribution rights and as I've said multiple times you can have the distribution rights to stuff you don't actually own and at least in the US you can use copyright to protect such rights.
So if it were the smoking gun people hope it is then the lawyers for Battletech would have already used it to get the case dismissed as their research teams should have found it long before now since I see nothing in the Arbitration Agreement that would make it difficult for a legal researcher to find/get a copy of.
I think you got the money dispute backwards.
Tatsunoko started a law suit against HG saying that HG hadn't paid them the total royalties they were due, HG said yes we did, and the arbitrator agreed with HG because Tatsunoko was effectively trying to claim they owed twice on some product sold through hg's web site, IE when HG bought/imported the stuff, and again when it was actually sold to end users, they were also trying to get monies based on electronic exploitation by claiming they owed for video, vhs, dvd, broadcast showing etc. which HG pointed out they had never charged for and were aware HG had been profiting for in the past.
the Arbitrator in what I saw essentially agreed that HG was more in the right than Tatsunoko regarding those aspects but reiterated that the 2003 renewal/ reissue of the distribution rights specifically that HG had from Tatsunoko specifically excluded the 41 characters because Tatsunoko as determined by the Japanese courts DID NOT Own those rights to license them to HG.
which means that the arbitration specifically acknowledges that the 41 are NOT part of HG's inherited distribution rights from Tatsunoko something that has to the best of my knowledge NOT been specifically acknowledged in US courts previously, because the US courts hadn't had that ruling from the Japanese courts brought into evidence.