I wouldn't mind a 64-bit version, if there's a significant performance increase.
But am quite happy with the 32-bit version, and the boxing we have now.

Having the option for a 64-bit version, with Joe Multiboxer, would be my preference.
As you said, its the least amount of work, as it is closer to 64-bit (code-wise).

And the current version of IS Boxer rocks; it will more than just tie us over until JMB's release.