If a draw or stalemate, the holder of the beast retains it.
Let's not make this difficult.
Get 50 plus 1...
If you can't defeat the holder, then you do not get it. It is I think that simple.
Goal is to defeat, if not the holder has continued to protect it.
If Sasuke had not survived C0, can it be argued that Deidara beat Sasuke? Or that Sasuke beat Deidara? It is clear when there is a winner at the end, but it gets less clear otherwise. In an IC match it would obviously be a loss cause, herp a derp, you just killed the biju too, but in an OOC match such things are hardly a concern.
In the case of a draw, recall, the champion did not fend off the challenger either for all intents and purposes, by definition. If the champion gets to keep it then that is the same as saying that the challenger loses, not really a draw.
Semantics aside, for OOC challenges, it might be best to discourage suicide attempt from BOTH parties. If a host can get away with both dying and he/she keeping the beast, he/she might try to kamikaze both participants. So what occurs should depend on who initiated the suicide; the challenger or the champion.
My battles with Ichirou (especially the first one) nudge me in the direction of forcing the judge to declare a winner, even if by a small margin. Let there be no draws to begin with. I know how the word "forcing" sounds but if we can get the judge to declare a winner based on how the two fought, I think that could wrap this issue.