A key character is coming back, and my money is on that character being Human Target rather than the late lamented Tommy.
Sure, Colin Donnell will be back, but my money is on the man wearing Tommy’s face actually turning out to be Human Target pretending to be a Tommy who never died.
Presenting some random civilian as the Green Arrow probably wouldn’t work; presenting Oliver’s meant-to-be-dead best friend as the Green Arrow gives Oliver enough of a connection to the case that maybe his lawyer could get away with arguing a case of mistaken identity.
All of this said, the Tommy who appears in the next episode is probably not going to be the Tommy who died in Season 1 or even a resurrected Tommy fresh from a dip in a Lazarus Pit.