If somehow alts were banned, you'd see more village activity, but not much. Considering the fact that no one is forced to specialize when increasing stats and pretty much everyone can be a "jack of all trades" and have access to most materials without any other person's help, banning alts wouldn't do much other than prevent "mining alts" and extra storage room.
If specialization was a part of the game, resources were scarce (types of crops and resources other than mines), and alts were banned, I'd bet you'd see a definite rise in active villages that actually function as villages rather than glorified tree houses for you and your friends. People would value their characters a lot more since there would be no option of using another character you had set aside.
I also believe that forcing people to one character an account would be an effective way to stopping a large amount of alts(if you wanted to do so
), as I assume in general people (always an exception, I know) don't want to go through the effort (although minimal) of making an account, logging in each time you use it, etc. But
