Interesting that you bring this up. I have two AR-180's, that I bought new back in the day, and so I may be in a position to comment.
The AR-18 was designed as a lower-cost alternative to the AR-15, using stamped-and-welded sheet metal instead of forgings. The idea was to sell to third-world countries which couldn't afford AR-15's for their militaries. The obvious roadblock there was that the Soviets were practically giving away AK's to those countries at the time. The effort to sell the AR-18 overseas ultimately failed.
Armalite's opening to the U.S. civilian market came circa 1970, when Colt temporarily pulled the AR-15 off the market to address the hammer follow-down issue. (Removal of the disconnector could result in sporadic automatic fire.) During that hiatus, Armalite had some success selling the semiautomatic version of the AR-18, the AR-180. When the AR-15 returned, sales of the AR-180 dropped off.
There were three manufacturers of the AR-180: the original Costa Mesa,California, plant, Howa in Japan, and Sterling in England. Of the three, Sterlings are the most common and also the worst in quality. I have a Costa Mesa and a Howa, but I refused to buy a Sterling (at the time) because of the dropoff in quality.
Overall, the stamped-and-welded AR-180 is inferior to the AR-15. Especially now, with AR-15 prices being so low, it's hard to see how a reintroduced AR-180 could compete.
The main advantage of the AR-180, as I see it, is that the bolt carrier and the buffering mechanism are entirely contained within the receiver, and this allows for the folding buttstock. The piston mechanism may or may not be an advantage. On the minus side, magazines are proprietary. Standard AR magazines can be modified to work, but this is a kludge. (I have to say that Sterling did make some good dual-use steel magazines. Their 40-rounders are some of the few 40-rounders that function reliably. You would have to pay at least $100 for a Sterling 40-round magazine, if you could find one.) Also, the bolt catch is fragile. If it breaks, it's almost impossible to find a replacement.
If you want a piston-operated gun, with a folding stock, that takes standard magazines, the Korean Daewoo K2 is what you should get. However, one that I saw this weekend at a gun show had an asking price of $2,500.
If someone wants to re-introduce a retro design, they would do better to bring back the Daewoo than the AR-180.
ETA: The AR-180 has a unique dovetail mount for a scope spot-welded on the top of the receiver. (On my Howa, this is misaligned so as to be unusable.) This was originally for a dedicated scope with an integral mount, similar to the original handle-mounted 3- or 4-power scopes for the AR-15. Aftermarket rails are now made that mount on that dovetail.