Actually, the only thing that the cheater needs is the time when the round started so he can join the pool.
Which pool does not provide...
You will not only need to hide the number of shares but the round starting time and the number of shares one accumulated in the given round (otherwise the cheater can connect one of its miners and see when the counter starts from zero).
Of course, I see no problem with hiding this.
This way you can effectively turn off all the statistics and publish only "pool mining digest from yesterday".
Not exactly. For now I disabled some numbers completely (expected round reward or worker shares), but I plan to reimplement this from round-oriented to time-oriented stats soon. So you will still see how many shares will miners does and so.
It will also be unfair to anybody who wants to join the pool (and not cheat) because joining midround is unfair.
It isn't unfair. Everybody have the same probability to hit good or wrong time to join the pool. Also don't forget that 99% users don't care about this when connecting the pool. Until you don't perform cheating, your loss from connecting in the middle of the round are almost zero.
he may estimate the probability that you found the block
Nonsense. You cannot say who find the block by listening, for example, #bitcoin-monitor.