Firstly, eliminating a meeting would loosen their control and also remove one opportunity to receive contributions...there is no upside for the GB in it, so it ain't gonna happen.
But, if some miracle were to occur, I'd say the first meeting to go would be the Public Talk. Well over 90% of the public speakers are mind-numbingly dull and couldn't reason their way out of a wet paper bag.
I could see a combined Watchtower Study / abbreviated Service Meeting on Sundays, and a School / Book study on one other night of the week. Maybe even a mini-school in CBS location homes...most people hate giving talks in front of 80-100 people, and it would cut down on nervousness in smaller groups.