just going to weld a gusset in each corner
I remember back in the mid 80's I think, could of been earlier, when the BMX style bikes came out the head tubes were the weak link on cheaper bikes. A lot of those bikes would crack just like that at or around the head tube.
So the first thought of manufaturers was to gusset the tubes together that joined the head tube. Unfortunately, all that did was shift the stress point to the ends of the gusset and breaks were common at those points. That in fact made them more dangerous or subject to catastrophic failure.
Just throwing that out there for you to consider. Ultimately a good BMX bike could not be made cheaply and simply corrected by adding a gusset. It just may be the wrong material to depend on is my thought.