A COUPLE of Ideas...
I have, not a champion design, but a champion request. This is a tad long, so if you must, TL:DR at the end.
Part of the allure of this game is the dynamic backstories and histories of the champions, and I think that you, Riot, have done a _fantastic _ job in recent times, not just giving us info-packed bios of the characters, but actual experiences and adventures that they embark upon. Most of us probably fantasize about what other epic stories the characters are involved in, but even more important than what they do is _who_ they do it with.
When it comes to backstory, I am most interested in the relationships between champions. I also _know_ that many, many others agree with me. The public approval of the Bilge water and Shadow Isles events was deafening, because it solidified the relationships between champions. Ever since  got reworked, I've seen so many comments saying "But how does she meet  now?" Because their lores were intertwined.
I've also seen the _somewhat _ amusing shipping frenzy that captures this community.  and  ,  and , and , and, and whatever other bizarre ideas people cook up. Seeing all of this shipping made me realize that there are *almost* no married couples in this game. Almost, because  and  are married, but theirs is a marriage of political advantage, not of love, as is clearly stated in their lore. That itself is an interesting aspect of the game's lore, but it's not what I had in mind.
I would love to see a genuine married couple, in a loving relationship, as two separate champions in the game. I think the dynamic of their story would bring a whole new character to the lore of Runeterra. And even ignoring their actual story, imaging what it would be like to have both of them in one game! If they were both on the same team, they would be united in battle, and either would give their lives for the other (At least, any decent summoners who cares about their happiness ;) . They would undoubtedly have special taunts/jokes for each other, but maybe they could even have a special effect, like slightly altered ultimates, or a small Easter egg buff, like plus 1 mana and health regeneration when together. But when the man is on team Red, and the woman on team blue, the play turns from comedy to tragedy. Their hearts would wrench at the thought of having to hurt their loved one, but they would have no choice. This would also be a great opportunity to create a truly deep story for why they joined the League. What drives them so strongly to join the League that they would endure having to kill each other on the field of battle?
As most of us know, a successful married couple usually includes two very different people, so by no means would these two champions be interchangeable. Perhaps the husband is a support champion, while the wife is a marksman, allowing them to cooperate fully when on the same team, and to be forced to fight more regularly when on opposite sides. Perhaps the man is a technician, who uses hextech guns at range and hextech staves up close, whereas the woman is a gifted sorcerers that uses magic at all ranges. Perhaps (And this would be kind of funny) their kits could be designed to be _really bad_ at working together, making their married life more difficult. For example, the man could be all about locking down all enemies around him, but then the wife keeps knocking them away in an attempt to save him. And if one was a mage and the other ADC, then they would always be competing for kill gold, and they (the summoner's at least) would rage about how they need more support.
My final request on this note is this personal note: Assuming that you make the right decision and start designing these champs, please make them as unsexualized as possible. Many champions in this game are oversexualized through the clothing/armor that they wear and their quotes, especially the female champions (Though  makes me uncomfortable, too. JK, he looks great now, btw ;) . This coming from a man that wants to give back some respect to women, please make these, and really any future champions, a little appropriate. These champions don't even need to be young, really. They could be a middle aged couple if you wanted, your choice.
TL:DR: Please give us a married couple, two separate champions that are married in the in-game lore.
Please give this serious thought. League is a great game, but It could always use even more character. I hope this is one way in which it can be improved.
Cheers.
Edit: Unbelievably, it looks like Riot is doing exactly what I asked off with these new bird champions. Now they may be siblings, and honestly I would be fine with that, but if not, I am thrilled that they are being added into the game.
Also, ignore anything in the above post about the institute of war and summoners. I learned shortly after posting that they no longer exist XD.
