The relative date slicer (a Preview feature as of June ‘17) gets us close to this with the ’This Month’ or ‘This Year’ settings. That is a dynamic date selection that updates based on the current system date. We plan to add a ‘YTD’/‘MTD’ option to specifically select a range from the start of the month/year up to today, hopefully that’ll address the remaining requirements!
Checking with Will Thompson and moving status to backlogTim Heng (Excel MVP) commented
Brilliant idea, great mockup that clearly highlights the benefits. The only thing you're missing in the DAX Editor is a "check formula" button. I also suggest that you cross-post this into the Excel Uservoice site as well, because the Excel measures interface, while better than the existing Power BI one, could also be improved in this way.