Quality controul has been going downhill for some time. There have been serious issues with pats like receivers and bolts, and my understanding is that, knowing about the defects with their bolts, in the past they've swapped bolts from surplus parts kits with theirs for complete rifles that they sold, but I don't believe that they do this anymore for want of such parts. LMT no longer makes their receivers, and their in-house production isn't very good. I believe a few other parts have had issues, and their magazines suck. It's unfortunate, because they are the only name in the game right now when it comes to complete new-production FALs in the U.S.
Honestly, if you're willing to go through the trouble, you can get an IMBEL parts kit in the $500-600 range, an IMBEL or LMT-made DSA receiver for about the same, and get it assembled and refinished by a reputable builder for not much more than what the complete rifle from DSA will cost. If you can borrow the tools and get some instruction on what you need to do to build it yourself, it might even save you money compared to the DSA.
For barrel length, you can get the IMBEL barrel cut down or sell the full-length one and buy one already cut down. The gas port will need to be opened up. I would caution against a 16" barrel, as barrels that short can sometimes be problematic with the standard gas system, even with the port opened up. FN's "super short" length, also made by IMBEL, was 17.17" (436mm), which is nearly as short as you can get it and have reliable function consistently from rifle to rifle, and the shortest length that allows the compatibility of bayonets and rifle grenades with the front sling swivel on a bipod-cut barrel.
If you want to save weight on a build, you can replace the lower with a DSA aluminum one (these still are GTG AFAIK); won't save as much as genuine FN lightweight stuff (the alloy used by FN is a bit lighter, and the pistol grip stud, recoil tube, and RT plug were all made out of the alloy, while DSA's are steel), but it will cost way less and still save substantial weight. In that case, get an LMT-made DSA receiver that matches the cuts on the recoil plate, either Type 1, Type 1.5, or Type 2. DSA's titanium combo devices so far sound decent enough and will help save more weight, as will DSA's handguards (and contribute US-made parts), which weigh about 3-4 ounces less than most OEM plastic handguards. There are other aluminum parts to be found as well, such as top covers, trigger guards, pistol grip nuts, magazines, etc. For ergonomics, I think using an FN Minimi/SAW pistol grip and a DSA or modified Commonwealth extended selector is the way to go. I also like the StG-58 plastic stock, which gives a bit higher cheek weld and weighs less.
Whatever route you choose, stick with surplus magazines or Moses magazines.