Could you make filter to check win rate for ranked solo Q, ranked party Q and unranked?
If I'm correct checking if a game was party or solo might be difficult with dotabuff API (game needs to be parsed).
Checking stats between ranked and unranked would be a great function to know if you win games with mates in ranked or unranked.

Also if the app is popular you could make notes visible to all if selected. It would be some kind of a reminder for all players that someone is toxic. It could backfire with some angry mobs or bots, but I think it would be interesting.

Can you make somehow synchronizable between different PC or easy to copy?
I switch between laptop and PC.