Aside from this lawsuit, many people, on all three sides lost and suffered much in that war. IMO, Germany was partially to blame by recognizing Craotia before any framework vis’a’vis Serbian and Bosnian ‘rights’ were set forth.
The war in Croatia had been going full tilt since August.
You'd do better to look at what was happening with the Yugoslav Federation in the late '80s, to discern the cause of the wars in Slovenia, Croatia, and Bosnia.
As to this particular lawsuit, it has about as much hope as one brought against the US government by German refugees from Silesia, based upon the Lend-Lease program.
Which is to say the only people who stand to make anything here are the lawyers, assuming they're not working on contingency.