Incremental Refresh Workaround

With incremental refresh not available in Pro, we're working on a workaround to reduce impact on server of refreshing 2 years worth of data each day

Approach is we have a fixed data source for last 23 months that does not refresh as part of load

Then another table which contains current month

(Each month we have to manually refresh the fixed data source)

I can create a new table with a DAX table expression to bring these together, but to replace the existing table it will be far easier to use PowerQuery M 

However, when I use PowerQuery to reference the other tables it refreshes them again, which defeats the point

Is there a way to amend a table, which is currently using SQL data, to become a DAX table? 

Thanks