I think 25 is too many, because I think it would be silly for something like this to spill over into the beginning of the season (and delaying the season shouldn't/wouldn't take precedence over something like this). This is something that could be prepared to start almost right when the playoffs end, but I still feel like a top 10 max (even 15 is a little much, as not all off-seasons will/should take that long).
These concerns, of course, are directed towards the idea of having 24 hour voting periods that determine the order.