Mid-age, since you and others already know the rifle's pedigree there is no harm to be done to anyones feelings at this point. For the sake of info, I'll go on and offer a little more background going back about 20 years on these 'tankers' and others. Namely the so-called Gibbs rifles since it came up.
Back then many of us here were then on the Gun and Knife boards followed by its successor Britishguns.net until shortly after the passing of our host, Mark Bitting.
Val Forgett Jr. himself was on the boards with us and he himself gave us the lowdown on what his commercial carbines really were. Mind you, he was defending against backlash for chopping up rifles.
The rifles were said to be rejects, modified because they couldn't pass muster to be sold directly as surplus. Original conditions were that bad or so we were told. They were not modified one at a time but in huge batches at low cost to get them to market at a price which could still profit. They are refinished parts guns made with both old and NOS surplus bits.
Another point of conflict was the fact the rifles were unmarked in regard to who did the work unlike the well marked Golden State/Santa Fe "jungle carbines" or the Jovino like-new builds...which are identifiable by traits and serial numbers.
The Gibbs name had been bought out earlier by Navy Arms and was used strictly as a recognizable trade name by this point. Nothing resembling the old and honorable company which once stood behind it. (Just like Curtis-Mathis televisions and other trusted brand names)
There were a lot of problems back then in regard to QC. They were hit or miss from function to finish. As Val told us on open forum, try them before knocking them so some of us did. I picked up three duds myself from disgruntled owners. I was able to swap parts and do some tweaking to get the rifles to perform. Others did the same. Most were refinished as that would come off staining hands, face, and clothing when used on a warm humid day.
By now, those duds which weren't stripped and sold for parts have probably been fixed along the way. There may be some which were tossed to the side or buried in the back of the safe which may someday resurface. Those are the ones to be wary of.
The rifles have always been notorious for being unmarked. Many suspect nefarious reasons behind that given the overall poor QC of the parts guns and misleading ad hype of the time.
The "tankers" such as yours I am unsure of some of their commercial origins. I don't recall them being a "Gibbs" offering but some were said to be sold under the Navy Arms label. Doesn't matter much at this point anymore. So long as yours works and you're pleased with your nostalgic looking carbine then all is good. As you said, given its history you are free to do whatever you need to/want to in regards to upgrades and improvements and that's a good thing too.