My idea was manually by server operator. He can automate some parts of it but some work would be probably required. Idea is that one man and few scripts can do work for the rest of pool users...

About that "switch from sha256 to scrypt"... How about this: "pool" can consists of 2 pools - one for sha256 and one for scrypt. Miners will mine at both of them, but based on current coin one will be always down...
Or any other working solution... definitively feasible...