well there is 1 little thing that you haven't thought of. People with lots of rares and score could simply give away loads of electrum and rares, for example several people got over 1M electrum they don't have any use for. This means we coudl end up with noobs that got 100K electrum and all rares, making bronze extremely hard etc etc.
I did think of that and basically just don't care.
Why not limiting the ability to get a reward code to once a week per account? If you would need more reward codes per week because of inofficial tournaments, you could still use alts. But you wouldn't be able to give a noob 100 000 
or 6 of a shard in a moment just because he asked for it.
Time limited uses is a great idea. As with everything, the specific numbers are certainly debatable, but I think it's a great idea as its base. As far as the specific numbers go, I'd probably do something more like 6 codes/week (at least depending on what the value of the codes settles on) allowing people who wanted to do so to run a weekly tournament with 3/2/1 prizes. However, don't really care about the exact levels when it comes down to it - whatever people think is balanced is good enough for me.
ummm tell me the point of having a bronze alt again? Other than for fun?
Just fun. Some people quite like submitting arena decks, and alts are the only way to submit to the lower leagues once you've leveled past them, and the lower leagues are (imo) more fun to submit to.
Also, I have played
a lot of the lower leagues and I really don't see an existing problem with people trying to create overpowered accounts to screw over all the newbies or whatever, and as has been pointed out a number of times, there's already far easier ways to do that than this if someone were so inclined. Besides, if someone really wants to make life difficult for the newbies in bronze, you don't need either rares or money to submit mono aether, ghostmare, etc.
