1. This one is simply for the sake of organization, making it easy to tell who intends to compete and who doesn't. Also, this is necessary for any of the rest of my idea to work, since we need to know the names of the users and what alt they intend to use.
2. If the ladder would reset at the start of the season, I suppose this becomes moot. It was purely for the sake of the clean slate.
3. Not allowing non-registered alts to ladder as a whole basically eliminates sniping as a whole, as it would become incredibly difficult to maintain a high rank AND snipe. If you choose to lower your rank to snipe, then you can't just switch back to a high ranked name, you're stuck where you are until you work your way back up. It's just cumbersome and no longer worth the effort.
4. This is an issue, but honestly, this is pretty much mandatory to prevent sniping. It's between being stuck with the same name for a few months or not having a ladder competition period. If the length of time is the issue, then we could always shorten the season to accommodate.
5. Well, obviously that would have to change, yes. And I think I did a fine job explaining how and what these would change in this post.