We've run into the possibility that some people might focus on mining empty uncle blocks, in which case the whole system can be abused/circumvented.
Sorry, but I did not understand, why the problem of empty uncle blocks is the problem of only uncle blocks.
As i know this problem exists even in bitcoin blocks.
As far as I know, those (evil)miners downloads only the title of the last (father's)block and mining their own empty blocks without bothering with the analysis of transactions added to (father's)block. (Evil)miners makes their blocks empty because adding random transactions from mempool without analysis of (father's)block transactions may cause contradictions between (father's) and (son's)blocks, which will make (son's) blocks invalid.
Simply: either you waste time and analyze your father's block, either not, but then you should make your own empty so that he does not contradict the father.
If so, could not this problem been solved by adding "hash-whole-father's-block" element in Proof Of Work similar to"hashwholeblock" in spread/zillion coin?