What they want and what they get are 2 different things. If it is a single shot system there is nothing they can do about it. No different than no gas tube.
Intent is a pretty big word. Just ask Comey and Hillary. She didn't intend to break the law so no charges..... And it's now in the public domain from the highest level of law enforcement. I put a 525 HP engine in my car. Does that mean I can be ticketed for speeding because they think I INTEND to speed?
I really don't want to argue. The posts others have made on here regarding AR pistol registration and inspection are numerous and often very deep with lots of back-and-forth comments. You should research those.
My understanding from those posts is HPD can, and does, do whatever they want as far as setting specific standards for what mods are acceptable and what's not.
As far as intent goes, the standard normally enforced by Hawaii when addressing firearm modifications is they must be done in a way that requires at least some amount of time, effort and tooling to undo the mod. Example: Anyone can install a flash hider to make their 14.5" barrel the legal 16" length, but Hawaii requires that it be pinned and welded. Is that permanent? As far as HPD is concerned, the time and effort needed to remove it makes it so.
Our laws are subjective, vague and based on ignorance of firearms. Arguing what someone tasked with enforcing the laws will decide (or is allowed to decide) is pointless. If your opinion is, "If it is a single shot system there is nothing they can do about it." I wish you luck. I can only speculate what HPD's response will be.
Please purchase the BCG and post what HPD decided. It would be educational for all concerned.