ok let's stop this bad information before it gets worse. I am a textile engineer by profession and do development work with various scuba manufacturers as well as designing bullet proof vests, FR fabrics for aerospace, and structural composites.
Denier is a unit, it defines grams/9000m, and has nothing to do with any sort of fabric other than defining the size of the yarn used to make the fabric, so please do not refer to anything as "denier" because it doesn't mean anything at all. This is equivalent to calling your scuba tank "cubic feet" or "liters", it literally means absolutely nothing in relation to what you're talking about. Every fabric has a "denier" based on the yarn used, so saying denier nylon means absolutely nothing other than some sort of aliphatic polyamide made by the DuPont corporation. Nylon is a tradename for that polymer, similar to Kevlar, Nomex, etc.
Lower denier numbers indicate a thinner and generally lighter fabric, think parachute cloth, vs. canvas, parachute uses very fine denier yarn, canvas uses very large denier yarns. This has nothing to do with durability of the fabric though higher deniers usually have better abrasion resistance because they have more material to wear through *think tires with deeper tread blocks lasting longer than not so deep tread blocks*. The fabric used for outer wing covers are made out of Cordura Nylon in almost all cases. These are SOMETIMES not always coated with an impermeable membrane, usually polyurethane on the inside and they are ultrasonically sewn or RF welded *basically the same end result, slightly different process* to seal the seams, then stitched for durability. Inner bladder materials if used are made with urethane which is a colossal PITA to deal with to actually make an airtight wing. You need very expensive equipment to successfully make a professional looking wing that is truly airtight. You will not be able to get a true airtight seal without using RF welding equipment or ultrasonic sewing machine. You can get close, but not close enough to use for a BCD.
1000D Coated CORDURA® Nylon Fabric
This is the material used for some BC's, it has the impermeable membrane and is available in whatever color you want. The biggest thing will be getting the seams airtight, and I can guarantee that it can't be done reliably without RF welding or ultrasonic bonding which actually melts the two layers together. Very little likes to stick to the polyurethane backing, and if you use a sealant, you will have trouble when you go to stitch it and it will look funky. Not trying to discourage you from DIY, but based on how little you know about the material and how it works, I'm going to assume you won't be able to bond the seams properly and don't want you to have a constantly leaking bladder which is dangerous.