some boards have been built and sent to friends to play around with.
Depending on who makes your PCBs, the NSMD (non-solder-mask defined) lands for the staggered BGA package will or will not work. for NSMD you'd usually have more stopmask recess around the pads. Since these boards are really cheap to make I ordered a lot of them and graded them under a microscope.
If your PCB manufacturer uses a maskless process, chances may be better that the lands are well-defined.