Conditional use of pre-aggregated series

I have a metric with tens of thousands of series and 4 labels.

power_consumption{dc="$dc",room="$room",rack="$rack",server="$server"}

I have pre-aggregated series per dc/room like this :
global:power_consumption:sum{}
dc:power_consumption:sum{dc="$dc"}
room:power_consumption:sum{room="$room"}

Aggregation per rack is always less than 100 series so no need for pre-aggregation

I have set chained variables for my dashboard for all the labels and that work super well, but 90% of the time I will load my dashboard and see only the global or dc view and I would like to avoid having to aggregate all the data at query time and to rely on pre-aggregated series to speed up my dashboard.

Is there a way to do this conditional switch of metric name based on if variables are defined or not in Grafana. Maybe by defining several #A, #B,… queries ?