A felony conviction for violating the MA AWB, jail time, federally prohibited person status for the rest of your life, lose your job, maybe lose your home, to say nothing of what the prosecutor might say to the jury about how you used an evil, illegal, extra-killy gun while trying to convict you on criminal charges for the use of force incident.
Your lawyer can hopefully find some wiggle room about whether or not your use of force was necessary. But if you've got extra killy illegal features on your post-ban, that's simple factual possession issues (post-ban serial number and it has a threaded barrel with a non-fixed muzzle device, or unpinned collapsible stock) and it's a slam dunk felony conviction for the DA -- you're effed and your lawyer will work hard to convince you to take the plea deal felony conviction with less jail time.
Edited to add: the consequences of possession a post-ban large capacity weapon with evil features is 1-10 years in prison:
Full text here:
General Law - Part I, Title XX, Chapter 140, Section 131M
In my opinion, it is absolutely not worth it to violate the MA AWB. The risk is too great. If you get caught, it would be a slam dunk conviction and it would change your life dramatically for the worse. I understand that some here on NES disagree with me.