I thought of that, but Roy wasn't really being Batman. He was letting Bruce take control of his body so Bruce could continue to be Batman. As far as I'm concerned, Bruce using Roy's body as a puppet doesn't count as Roy being a whole new Batman.
Yeah, I ended up thinking of this story too, but not until today...
*spoilers for the story 'blind justice'*
I don't know, I would say it counted in a way. If he hadn't volunteered his body there would have been no Batman out there, he was a hero for putting his life at risk in Batman type situations, so in essence could be considered to have taken the burden of the role of Batman on his shoulders. Ok, it was still Bruce's mind out there, but at the end of the story roy's mind comes back into control of his body whist in the middle of a Batman situation and he dies as a result, so he was there as Batman in mind and body for that.
Anyway, Mister J basically covered all the straight by the book Batman take overs, there's no harm in listing other tales where the notion is explored in 'What if?''s or mind control or whatever, it's just a bit of fun. unless of course the OP is doing a PhD on the subject, in which case I'm sure he will know to ignore certain tales in his thesis.
edit to add:
the OP wanted the reasons why other people ended up in the Batman role, so...
in Detective comics annual 4 when Tim Drake takes over, it's because Batman breaks his spine falling down a mountain after his final confrontation with Ras Al Ghul.
In 'Blind Justice' Detective comics 498-500, Bruce Wayne is shot in an assasination attempt putting him in a wheelchair temporarily, which leads to him using Roy Kane's Body.
Batman 666 - reason not given, we are to assume Bruce is dead by that point I think.