Snake, the articles and reviews I have read said that the upgrades were for reliability and accuracy. I think the rivets are for receiver rigidity and stability, making the rifle more accurate, but do not affect safety as the bolt still locks into battery the same way on both pre and post ban. Bushmaster is very safety conscious-they already have their fill of frivolous lawsuits because of the DC sniper, they don't want any more.
I would hang on to it, whether you upgrade it or not. It is a sure bet that the next round of anti-gun legislation will ban the M17S by name along with all bullpup designs. And with gunsmiths/M17S gurus like Kurt's Kustom Firearms around, you can always keep it looking good! I would ask Kurt's opinion if you are worried about it.