I dont think the system IR is thinking about would reduce the load on servers to a big extent. Now the demand for AC Tatkal tickets will go up.
Like you said, IR could try something like: for trains starting its journey (from originating station) between 00.01 to 12.00 Noon, the CK booking can be opened previous day at 10.00 and for trains starting between 12.01 to 23.59, CK booking can be opened at 11.00, or something like that.