It's not right how some champs get annual releases while others like 
have been waiting 4+ years.
Here's a solution. Get a big list of all the champs and organize them by how recently they received skins of any kind.
Then focus on them in an appropriate order.
Generic themes like chem tech tryndamere could have easily went to other champs
I think this would help as a guideline for where to focus their creative thoughts, but they are human beings - not a factory or computer. They have favorite champs, favorite styles of art (ex: arcade or darkstar or some other type) and can't be just made to HAVE TO come up with a skin theme for a specific champ. It's like telling a musician they need to write a country song about a farmer one week and a rap song about a breaking up with their girlfriend the next week. Some MIGHT be talented enough to do it, but it probably wouldn't be pretty or have their whole heart in it.
That would limit their profits a lot, to almost -50%, some skin themes fit to specific champions a lot more than others and people would buy them faster, if they made skins based on which champions have less and don't fit them it would feel forced and a bad marketing move.
For example if there are 10 skin themes that fit perfectly for Ahri
which is a popular champion then they will give them all to Ahri instead of an unpopular champion which has less skins and the themes dont fit him/her.
