Streaming worlds is a great feature, but it's going to take a lot more than adding threads to BlitzMax to make it happen. It's a lot more work than I think people are giving it credit for - the language really needed to be built with it in mind from the start rather than trying to tack it on now.
BlitzMax2 is probably your best bet for this. :)
BlitzMax2 is probably your best bet for this. :)