A couple of things:
1) There is enough budget already to do the 3rd disc. The question of the coin is one of freeing up budget to do other cool things.
2) A strange side-effect of the way you're going to get to rank stuff to use up the budget is that you could vote to dump the coin now, but later (after someone does some design work) vote to add it back in again (or something cooler that someone comes up with).
3) The idea of doing the coin as an add-on is entirely possible. I'd like to experiment with add-ons.
If the coin was dropped, would it increased the chances of a re-dub or adding the soundtrack on CD?
No way we'd be able to afford a redub. The CD is probably something that would be possible, depending on licensing issues. But since the Japanese CDs have been available for years, is that really a good use for the budget?