Rather than try to get the SCYSA to allow teams to play up but declare normal age before the state cup, why not simply request to play both U13 and U14, qualifying results being the U13 games, then play at age during the state cup. Might be an easier sell. The U13 age group remains in tact, and those teams seeking higher level play would therefore get the increased competition in the state. Might want to add that you'd be willing to pay 2 entry fees.
Sometimes it's better to look at the good of the whole rather than your own affiliation. "The needs of the many outweigh the needs of the few". Often times when you look for a win-win solution, you're able to produce one that works.
Futbol, I believe the logic behind the SCISA allowing younger players to play Varsity has more to do with numbers than anything else. Many of these schools have entire high schools with less than most HS senior classes. I graduated from a 2A school with about 210 seniors. Most SCISA highschools have less than that. The SCISA rule further puts a stipulation on physical maturity, with that decision resting at the school level. I've seen some of these SCISA middle schoolers play, and physically, they were able to play in the group. Is it fair? Maybe not, but that's an entirely different discussion. Does it help the players? I would say it does, as many have noted, training and playing with better players, produces better players.
Daddy, the answer is yes if they are US Club Soccer. US Youth Soccer doesn't prevent it, only requires paperwork.