Dont see why the T couldn’t operate it as two bidirectional tracks and have trains arrive and depart from both platforms like at Oak Grove, Alewife, ect. It’s annoying that trains could leave from either level, but isn’t directing passengers to the right platform what the T ambassadors are (should be?) for?
If your near HRT quality light rail can only manage headways unsuitable for even proper regional rail,
1) maybe, potentially, think about considering using 2 tracks,
2) Bustitute at least the Union branch to Leachmere to provide an actual usable service.
The current untenable headways seem like the T checking a box (yes you still technically CAN take a trolley to Union) rather than actually caring about providing useful transit.