There's no possible 'random' method of determining block rewards. Whatever mechanism you have in place will be cheated to hell in back. Just like with junkcoin.
This.
Any set numbers in the minted block hash, like the first or last 4. Example - 0001 to 9400 --> 88 LKY. 9401 to 9900 ---> 188 LKY. 9901 to 9999 ---> 588 LKY. 0000 ---> 5888 LKY. There's no way to predict that. Any questions?