@ICY now I think about it yes, the only thing that has not been tried or has happened yet is that the Dorje Shugden ban has not been lifted. Yes it is true nothing is ever impossible.
The thing is, history knows that the main person who founded FPMT and was instrumental to the formation of FPMT it was Lama Yeshe true and true. And the only reason a lama cannot manifest his buddhahood could be due to vows or promises that are broken. FPMT being the anti Dorje Shugden that is have become there is no room for discussion and no room to interpret anything differently from what FPMT dictates.
Hence when Lama Osel was training at FPMT he could not do the Dorje Shugden practices anymore, and that could have created much pressure and obstacles to arise in his mind. Mind you before Lama Yeshe came to the West his past incarnations probably also practiced Dorje Shugden. What Lama Osel had done parallels what Phara Rinpoche had done which was he went gambling, became a policeman and so forth, seemingly undharmic actions or so we are led to believe. The very people behind FPMT have some soul searching to do about Lama Osel their main founder's incarnation not willing to step up to the mantle of leadership.