First, let me say thank you for dedicating your time, labor, expertise, and funds to such a wonderful cause and such a fun tradition here on the Gang.
Second, I would think anything between 45-55lbs would be great. Keep the length long enough that guys with 29-30" draws aren't getting a lot of finger pinch. Doing this would put the bow into a huntable category for the vast majority of users. If you were building it for just me, I'd say 60" and 50-55 lbs would be ideal.
As for woods, I think it would be most fun to have woods donated or bought from other vendors or something. The more TradGang community that can be involved from materials to building the better. That's part of what makes the Hope and Faith bows so much fun. Horn tips would be a cool addition. I'd be willing to donate some whitetail antler pieces if I have some on hand of the right sizes for you to add to the build, although my stash is fairly small as of now. Feel free to PM me if interested.
It might be a good bow to try something new that you've had on your mind and debut it as a prototype whether its a new finish or shape of accent piece, or what not and then it could add a little something cool to be able to get in on the first of whatever feature offered at the St. Judes auctions. I'd say just build it for the average user of yours and have a LOT of fun with it.