The 10# trigger is also required....
(Apex Tactical can fix that, but I'm not sure how the MA authorities would react.)
The Shield currently comes with all the other requirements as standard equipment. You can remove the thumb safety and magazine safety devices, though.
My vote would be to use Apex's kit to improve the drop safety rather than remove it, but that's pretty easy, too.
So, presuming the folks who have to bless the thing in Massachusetts did so, it's compliant. Size-wise, it's not a lot smaller than the M&P Compacts, which have long since been acceptable (when equipped with a heavy trigger). A thumb safety is available on the other M&P's, too, but I'm not sure if the MA compliant versions must have them.
AFAIK, CA has the same requirements as MA when it applies to the Shield or other M&P series guns - about the only thing that can bite you might be the size of the gun.
Toledo OH used to have a list of "approved" guns that didn't include my PPK/S. They didn't want "Saturday Night Specials", so legislated out a lot of smaller guns, etc. That the PPK/S was selling for something like $400 at the time didn't seem to register.
DO ask somebody in MA about changing that trigger if you're thinking about it. It may not be legal to do so! Here in OH, there's no legal issue, but mucking with any manufacturer-supplied safety device may get you into problems in a Civil action should you use the thing. I doubt if anybody in OH would notice, but who knows....
Regards,