Issue:Merging items with different health. - We didn't do the item merging, as we didn't want the player lose his precious items as two 49% items would merge into one, which would prevent the player from repairing both for just a few repair. In reality, I feel that the annoyance of having 8 different stacks of laser turrets/walls in my inventory is not worth the rare possibility of losing an item or two.
While I agree with the reasoning, I don't support the outcome. In mods with extremely expensive buildings (Bob's mods for example) losing some of your buildings because you lifted them too early would be unnecessarily cruel, only because it is far far cheaper to repair the structure than build another one. If however the repair mechanic was changed so that to repairing the item cost the same (proportional) amount in resources as building a new one then that feeling of being ripped off goes away.
Suggestion:
Instead of having a specific "Repair Pack" that is the single, extremely cheap, all-in-one fix it, extend the inventory merging mechanic to be the repair mechanic. Have a wall that needs repairing? Just drop another wall on top (as you would do for a fast replace) and the HP of the items would be merged with the leftover remaining in your hand. Construction robots could go and pick up a wall and use that to repair instead of a repair pack, etc.