It's not "unsafe" per say, it's just not going to be anywhere near as thorough as what you can do with a chipped OBD1 ECU. You're not boosted though, so you might be able to get a decent enough tune with a piggyback if the tuner knows what he's doing.
Why don't you just ask the place that's going to tune it which system they recommend or prefer? That's probably what I would do...