Even if the 16th Amendment is repealed, we will need a revenue collection agency.
Also repealing the 16th Amendment will not change anything. The courts will simply reinterpret the constitution to allow the Federal Government under the tax clause and the commerce clause to do any damn thing it wants to do in regard to collection of revenue.
The 16th Amendment was passed during a period in which the courts were actually interpreting the Constitution in accordance with the original intent.
Today, not so much.
The 16th amendment did not legalize an income tax. Abe Lincoln had an income tax. What it did was remove the requirement that it had to be proportioned by state.
So, even if we repeal the 16th, Congress can still impose an income tax. They just have to let each of 50 states know what their fair share is, and then those legislatures go about figuring the best way they want to collect it in their state....a states rights, republicanism kind of approach to taxation.