Create Format Dax Function that keeps data type as a value

I have a use case where a user can select different unit types from a slicer (e.g. this could be currency, but in my particular case, this is for allowing a user to see energy consumption in KWh / MW etc.)

I am able to use the FORMAT() function within a SWITCH() expression to format the number of decimal places showing for each unit type (i.e. 2 decimals for MW, no decimals for KWh), however this only works for tables as the format conversion is to text - it doesn't work for charts.

Therefore, please may you look into creating a format function that allows the format to be kept as a value so it can be used in charts?