Glory is a kick boxing promotion, and that would probably end extremely bad for ADR there. Unless they did some mixed-rules fight. Either way, he would get pieced up a pure kickboxing match. Bellator is the obvious leading investor. Scott Coke took over a lot of the decisions in Bellator and he has been aggressive in obtaining big names. They have also entertained offers to Lesnar in returning to MMA, recently signed Kimbo, and are the sole reason we saw Rampage Jackson and Tito Ortiz on TNA television in the past couple years.
This makes total sense if they can work another deal out where he would appear both in TNA and Bellator. Bobby Lashley, King Mo, and Rampage Jackson all had deals like this. Jackson is back in the UFC though.