I have read many of the comments on this topic. I have also checked the list of rotations between now to about 2 months ago. I see that everyone is right, Riot has rotated the same champs every week. If I were to choose 7 new champs for next week's free selection, here is what it might look like:
Xin Zhao - a solid assassin champion that has been seen alot so he is familiar to most that play the Crystal scar. He is fast, has great attacks and is an assassin so can be played with stealth. He also doesn't seem too difficult to use which makes him great for new players.
Rengar - A ferocious figher that has both good support (slows, debuffs) and mean damage dealing. He does have some learning curve to him, considering the timing and skill required for his attacks to be most effective. There are some champions I have NEVER seen be used. Rengar is one of them. This free champion rotation would be a perfect time to showcase certain champions that have been swept under the rug.
Nautilus - This guy seems like a beastly tank type. Though his Riptide Shockwave seems to prove his potential as a fighter. His attacks are strong, ruthless and merciless. Nautilus is the champion you will choose as the one to carry the team when all else fails. A perfect representation into the free champion week. To show just how devastating the tanks can become.
Ahri - There are many mage type champions to choose from. And they are all viable candidates for the rotation. But many of them were also the low cost champs that everyone has seen or played before. I chose Ahri because she is the "petite" champion in the bunch. She is the glass cannon if you will. She can dish out serious punishment with the right skills and her spells can combo continuously. But she requires a team to stave off the hardier foes so she can set up the combo attacks.
Lulu - This is one powerful support champion. After reading up on her abilities and having personally seen her in battle, I can tell you that she can make even the toughest of opponents seem measely. With a perfect selection of spells that suit all champions she is a great champion to represent in a rotation week. She is also cute n cuddly, independent, and carefree. Remember we play this game to have fun, not just to win. Lulu brings that spirit of fun back into the game.
If you noticed I have put one champion of each champion type into the rotation so far. There are 2 spots left remaining. This is where we could either play wild card champions that can swing in various directions, or we can do fan-based picks.
If it were fan-based:
Draven - Great allround character with a moderate learning curve. Many people asked for him in the comments as well.
LeBlanc - LeBlanc is mainly support but can be a devastating powerhouse in her own right. Many people also suggested her and I would choose her also because she too has a steep learning curve and is a familiar face.
If the 2 spots were wild cards -
Talon - The Blade's Shadow, is a cunning assassin. Perfect for those who prefer to sneak in the shadows rather than stand their ground in a lane. He would make an excellent jungler or champion executioner. Talon however has a steep learning curve, but comes with deadly rewards as a result.
This last pick came down to either Sivir or Sona and the winner is: Sona. Why Sona? Some of you might say that she sucks or she is already such a low cost champion, or that we see her ALL the time in the bot games. But hear me out, Sona is a support, ranged champion with an easy learning curve. Perfect for beginners who favor staying behind the line of battle aiding his/her comrades. Sona may not seem like much but if it's true how we feel about her then she is an underdog. Sona is very different than Lulu and deserves some credit.
As you can see my picks were all about diversity, and spirit of the game. I chose champions who are vastly different from each other. This plays well to all types of gamers. I personally excel at the stealthy(Twitch, Akali) and support (Lulu, Janna) types. But my friends might prefer a big battletank(Blitzcrank, Nautilus) or a lithe female mage (Nidalee, Ahri).
There are still many other ways to diversify the champion rotations.
Based on Region (Damacia vs Zaun) Perhaps split it to 4 fighters from each area.
Good vs Evil (Garen, Sivir, Ashe, Taric vs Singed, Urgot, Vladimir, Cho'gath)
Nature vs Technology (Nidalee, Udyr, Volibear, Rengar vs Graves, Blitzcrank, Tristana, Caitlyn)
Magic vs Science (Ryze, Zilean, Ahri, Cassiopeia vs Heimerdinger, Singed, Twitch, Corki)
Race vs Race (Yordles vs Humans), (Poppy, Teemo, Rumble, Corki vs Caitlyn, Darius, Akali, Fiora)
Male vs Female (Gangplank, Draven, Shen, Garen vs Missfortune, Riven, Irelia, Katarina)
So many paths to choose, and so many champions to choose from.