Show Solo Rankings for DQ
It wouldn't have to be retroactive. It could just be from whenever they introduce it forward. While it would still be pretty shitty for solo players, it would make it way more predictive of individual skill. Sometimes you'll get carried by pre-mades, other times you'll get destroyed by them but the variables will be mostly the same for all solo players over sufficient games. Thus, the ranking shown would be about as accurate as the old solo/duo system (which was also slightly distorted). Implementing this would not harm queue times or do anything else negative.
Unless Riot is actually intending to obfuscate individual skill, there is no downside. It would be business as usual in every regard except that rankings would be more specific for those interested in measuring their own performance in an accurate way that can actually be compared to other solo players. Currently, you can't even compare players of the same ranking because the queue configurations can be so different. One guy can be Plat 3 playing only solo while another only 5-mans and it's a different experience/skill-set.