Skasi
I don't think the UI would be too bad - I'd just use the existing Puppy/Retreat functionality.
Let's assume it's
not a con (my preferred approach, but it makes the UI easier since cons create conflicts between resurrect/harvest)
1) Use the Puppy Goo logic for harvesting. That is, unit just stands next to wreck and auto-claims. Disablable with the On/Off button.
2) When the unit has harvest-reclaimed to max, the unit automatically heads to teh nearest
retreat point. Retreat works well here because tehre are usually lots of nanos near a
retreat point.
3) Arriving at the retreat zone, the unit spits out a feature that contains all the metal from the unit's puppy-goo bay. Spitting out the feature can be manually initiated with the D-gun command. Unit automatically avoids doing harvest/reclaim within a retreat zone.
4) If possible, give the unit support for the "reclaim" order even though the unit lacks a nano. The puppy probably needs that too.
5) The metal-lump feature also appears on death.
Either way, the point is that the Puppy provides precedent for a non-reclaiming wreck-eater and as much of the Puppy logic as possible could be reused here. The only difference needed from the Puppy for harvesting is the behavior when the internal bay is full - retreat-and-spit instead of spawning a new Puppy, and avoiding doing the harvesting within a retreat-zone. The only new "power" it has is the wreck-spit.
There, no new UI, and the unit behaves intuitively and automatically (as long as you set retreat zones).
Put it on the Duck the or the Koda or something. Some raider in a lab with a very slow con.