Layering is needed for hot days if you are in full costume...moisture wicking first layers, such as Under Armour, will keep you cool once you have sweat through your first layer. Also it will help to protect your costume which may not be as washable as your moisture wicking layer... We saw too many ambulances and heat stroke victims this year. Be careful out there cosplayers!
Please wear a bra with your corset (esp. if you are more than a C-cup!) Wear dance tights if you have a high cut short or skirt. It is good you feel sexy and confident in your costume, but not everyone is there to see your 'goods.' Also, people bring their kids during the day, have some grace and self-respect. Save something for the imagination - at least until after dark.
Just accept that in the crowds, elevators and stairwells, your floor-length capes will get stepped on, and your delicate wings will get bent or broken. Don't have a melt down - no one is doing it on purpose.
This is not a bad thing. It is awesome that so many people can share their collective passions for geeky things in the open - it was not always so. Having more people come out isn't 'ruining' Con. It is the attitude of those people who want to keep our world exclusive and don't plan their day (or weekends) with patience and joy in their hearts that can ruin Con for everyone. (And a*holes that intentionally drop things off balconies and injure people, but that is another story.)