It deffinately needs attention. However, since most the the structure is physically still there, I think that you may be able to get away with a patch. If you can get too both sides of that even better. Start out by mixing micro-bubbles, or silica powder to resin to make a thick filler compound, add your hardener, (or if epoxy even better, but mixing will have to be done quickly) If your using polyester, make it just a little hot as there is no daylight in there to help the catalyst. Then start with thin strips of clothover just the crack, and add layers getting progressivly bigger, untill you cover that whole biulkhead. Your going ot get messy doing this as I bet it'll be hard to manuver cloth down in there. Like I said if you can do this on both side much the better. Check it often for the resurgence of cracks, as this should happen before any failure.(Something that makes for a catastrophic instant failure after this procedure would likely do the same thing on a perfect hull) Hopefully you patche, combined with the large amount of bulkhead wich appears to still be intact will be able to dissapate and withstand the forces for quite some time. Another option might be to do the same thing with carbon fiber, it would be a lighter repair, but its possible that you want some flex here, I'm not that type of engineer so I'm not sure about that point.

Good luck, but do get some attention to that area.