I did not find how to point to predefined measures, but we are now using variables for each measure, so it would be easy to switch between them.
LET vL.ClientCost = SUM([Client Costs Field])
LET vL.ClientRevenue = SUM([Client Revenues Field])
LET vL.SwappableMetric = $(vL.ClientCost)
And in your metrics, you could simply use the variable value.
For example, My [Client Costs] metric would be $(vL.ClientCost).
Hope this helps!