If you station a spacecraft with enough counters that it is a creature, and you copy it with Taskmaster, Mercenary Mimic, the correct result under the rules is that the Taskmaster has 0 toughness and dies. This does not work on Arena, where Taskmaster ends up having the spacecraft power and toughness.

This is wrong, because the power and toughness granted by the station ability should not be copiable. It is a static ability that generates a continuous effect that applies in layer 7b:

721.2b. "{N+}[abilities][P/T]" means "As long as this permanent has N or more charge counters on it, it has [abilities] and is a creature with base power and toughness [P/T] in addition to its other types."

I reproduced the issue in MTGA by playing a The Seriema, stationing it up to 7 counters so it's a 5/5 creature, then choosing it with Taskmaster, Mercenary Mimic. The result in MTGA is a 5/5 creature, which as explained, it is wrong. It should become a 0/0 creature and die.

Attached a picture of the situation I described.