lunar assent vehicle as possible space tug at ISS

I was wondering if anyone has discussed bringing the future lunar assent
vehicle back to the space station. It seems to me they would make a great
space tug if they could have expendables replenished. There is a large
enough engine to do higher orbit missions and life support to have extend
missions. It could be retrofitted with for an arm and other need orbital
equipment after return. It just seems to be a waste to leave the first few
in orbit around the moon.

Suzanne Rathburn