Knife is older than I am, just wanting to get a handle on the situation. This knife is just like my rifle project, it was my grandfathers and made several cross country trips.
What's the brand on it. I can see in the photos it was made in japan, but can't make anything else out.
Either way, I say go for it. If nothing else you could delicately remove what's left of the handle, rivet a piece of steel on either side for new handles, and wrap it up in some paracord.
I did something similar to a romanian ak bayonet I got for 5 dollars. It's not a 'quality' knife by knife collector's standards, but I just it backpacking and camping and it's never failed me, yet.
On instructables.com they have a bunch of tutorials on casting aluminum, but, i'd still run steel down the center, since aluminum is a soft metal, and you wouldn't want it to break again.