The redesign is a complete new cradle from the roll cage backwards. A bit impractical for you I'd suggest.
I'd work on re-inforcing those pivot tubes where they are just welded to the side of the box section, and try and support the forward end of that tube with additional tube, or just some triangulation which picks up the top wishbone front pivot.
I don't have any pictures of either Tim Pages or Neil's (Arthur's) work which addressed this issue on their chassis', but they may be along with something for you....