The suggestion for members to divert all tithe to local church budget, would impact local church operations because it would shut-off the flow of funds not only to the GC but to local and union conferences as well.

Believe it or not, but most local conference expenditures directly benefit the local churches and their members.  For example local conferences fund 100% of the salaries and benefits for pastors, as well as a substantial % for church school teachers.  Local conferences also operate academies, summer camps, etc, on behalf of all of the members.

Likewise, union conferences operate colleges and revolving funds and some other services that directly benefit local churches and schools and members.

I am not saying all of these layers are necessary.  I am saying that most of the services they provide are useful to local churches and schools and members.