Tho having a place to store so many maps and allow users to download them 24/7 is very expensive and might lead to pay-to-pay which wouldn't happen so I think this whole idea is not an option
I guess they could put some download/uploading restrictions on players.
For example:
1. Players need to have an account that is 14 days or older to be able to upload/download maps. The account also must have at least 24 hours of logged in time.
2. Players can download a maximum of one map per 5 minutes.
3. Players can upload a map a maximum of one map per hour.
4. Players may have to join a "waiting line" to download/upload maps depending on the amount of players/activity going on at the time.
5. Players also have to enter a "CAPTCHA"
(or some other similar thing like that) to confirm they are not bots downloading/uploading map.
They could also add a couple more "banner ads" on the map downloading/uploading section of battle.net to help pay for bandwidth costs.
They could a system similar to sites like rapidshare, megaupload, etc.
Sure it'd be weird to have a system like that on battle.net but since they said major additions are coming to battle.net, and a place to upload maps and "link them to a player's account" would make "legit maps" more accessible and reduce the amount of potential map stealing and raise user-awareness of map rigged maps.
What an upload/download map section for battle.net might help:
1. Reduce potential for map stealing - Obviously, if a person uploads a certain map first, they get the credit, they get acknowledged as the map maker. With an easy-to-access upload/download map section on battle.net, this makes things easy.
2. Raise user awareness of map rigging - Lets take DotA as an example(since everyone knows about DotA). Because DotA has a
website which always have the "newest official" versions for the map, people who try to host rigged versions of DotA will have a low chance of getting players to play that rigged version.
Players know that the newest official version is always at that site, and if a "new" version appears anywhere else besides the official site, players know that it's probably a rigged version.
Lets take maps not as popular as DotA but gets hosted somewhat often but not everyone knows the official site of the map: Enfos, Gem TD, etc.
These are examples of maps that are played somewhat often but not many people know the official site of those maps.
That means people can get away with hosting rigged versions of Enfos or Gem TD(for example) because not many players know the official site for those maps or know which versions are official and which versions are not official.
With a map upload/download section on battle.net, map makers can upload their maps so that players can be able to easily find the official map and author they are looking for.
Anyway, if Blizzard does something like that, I think it'd help with the "map rigging" and "credit stealing" problem, since not everyone knows the official websites of maps and not everyone knows to upload their map to sites
(hiveworkshop.com for example) before hosting their map on battle.net
(to prevent credit stealing, also to have a place to upload official versions.