1. Yes. Multiple currency fundraiser would get very complicated. Single-currency fund-raiser makes much more sense to me.
2. Why would someone send money to a fund-raising address if they didn't want to participate? If they are paying the person, they would not use the fund-raising address.
3. Yes. We ran into this problem with the original Mastercoin fundraiser, where some people barely missed the deadline.

I can see why having a separate investment transaction would be helpful. I went ahead and added an "Investment Send" transaction. Then I realized I also should do a "Restricted Send" for sending from savings wallets and rate-limited wallets, so I added that too.

Thanks for pointing this out! I think it's a lot cleaner this way.