You are doing great medleyofcostumes, only one name wrong. Or.... "wrong" isn't really a good word. The official name of the "White Bicentennial" is "White Egyptian Bird". I can provide you with a list of original names if you want to.
You have pointed out an interesting subject. The matter of the chains. Now you have to understand that, although many belts do have a matching pattern, they are a totally different story than the jumpsuits. They were also designed by another man. Sometimes this fact is proved by the way some belts do not really match a certain suit.
It's also important to know that the jumpsuits were originally designed to be used without a belt. The whole belt story started because Elvis wore them privately and then Priscilla suggested him to try them on stage, which he already did in 1969.
As for the chains; Both the belt from the "White Egyptian Bird" and the "V-neck" were designed without the use of chains. There are no holes in the belt to attach them. This has probably something to do with the design of the suit itself.
As for the "V-neck" the designer wanted to keep the suit as plain as possible to create a resting point between all those elaborate suits. The same goes for the "Rainfall". This is also a very plain suit although this time the holes to attach the chains are present. But adding chains to it could have disturb the tranquillity in its design. It's quite possible Elvis at one point stated he wanted these chains because they gave him comfort. He always stuck his thump behind them which became some of a trademark.
But it never happened and this could have many reason. It is no use to go speculating about it. Fact is that even now, when the suit is on display, no chains are attached.
The "White Egyptian Bird" is not really a plain design but most of the "business" is happening above the belt, on the chest and back. Below the belt there is only just some pattern on the outside of both legs. This creates the effect of long legs to lead away the attention from Elvis belly. So there must be as little as possible below the belt. This also means no chains.
I hope I was able to help you out a bit.......