Sorry, but this would never work.
The whole point behind the Black Market is that it's all based around chance; hence why nothing is guaranteed and you can even get the same items multiple times.
It creates the same effect when using a slot machine, you just keep throwing money at the screen for a fraction of a chance of receiving what you want.
When you guarantee a weapon (face it, no one gives a shit about the other stuff), then people would simply save up their crypto keys buy a bunch of CoD Points, get all the new weapons, and never touch the black market again until new weapons drop.
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Also, let's say this system was indeed introduced, and let's keep in mind that Activision wouldn't want to see their profits diminish.
That would mean you'd have to increase the price of the supply drops, to compensate for the elimination of the above-mentioned probability that's the core of the Black Market system.
Some folks figured out that the chance of getting a weapon are <1 percent. or 1/100.
That would mean that if you'd give players the option to buy weapons straight out of the gate, you'd need to increase the price of the supply drop by a factor of 100 to balance everything out.
So, the price for a single guaranteed weapon supply drop would be 30 * 100 = 3000 crypto keys.
Or about 20 000 cod points.