This is one of those points where if you don't know the background, you can't effectively talk about what it is you're talking about. Your arguments sound good, I agree, and would be wizzer, except for the fact that y'all haven't a clue how it works.
Dikote, as a process, spreads a layer of crystalline carbon - diamond - across the surface of an object. That's not part of the surface, that's the entire surface. Why? And why doesn't the Wyrm think it appropriate to apply to armor? Well, let me quote directly from Shadowtech, the 2e sourcebook in which it's introduced:
DikoteTM
DikoteTM is a process that deposits a thin diamond film on any solid surface. Small volumes of methane gas are mixed with large volumes of hydrogen gas, then subjected to powerful beams of microwave energy. This creates a plasma, a super-hot gas in which all atoms are ionized. the plasma is then passed over the cooler solid target, forming a diamond film as the gases condense on the surface.
The diamond film imparts much more structural strength and resilience to conventional materials ... <game information clipped>.
Treated products also find use in the construction of high-speed bearings. Bearings treated with DikoteTM last in high-temperature environments where conventional lubricants break down, permitting the development fo faster, more efficient, more powerful engines and turbines...
>>>>>[ Not everything can be glazed with Dikote. The item treated must be able to withstand the heat generated by the plasma. This obviously eliminates cloth and plastic, which, unfortunately, comprise the bulk of casual armor these days. If you've got some of the heavier stuff or ceramic armor, getting it glazed is a great idea, if you have the money. ]<<<<<
-- The Smiling Bandit <Strikes again!/Ha-Ha-Ha>
Understand that your softer metallic materials, including bullets, aren't gonna survive this process; they're going to soften, distort, even melt under the heat of the plasma bath, and metagamewise, 'dikoting' your APDS rounds was effectively double-dipping. As well, it was generally accepted that the glazing process takes place in a closed container, not with something that's functionally a hand-held 'dikoting torch'; this means that your object has to be able to fit within the container, thus limiting the size of the object you can dikote. This means that no matter what you want to put the coating on, you have to coat the entire surface area of it - and thus pay for the entire surface area, inside and out.
Back when you didn't have a single rating for armor, you could distinguish what was able to be dikoted, armor-wise - anything that used ceramic plates for projectile (or impact) resistance. You'd dikote the plate, then put it into the armor, thus upgrading your armor by one. Nowadays it's a bit less specific, and while it's something to be left up to the GM, a good general rule would be 'hard armors only' - and in keeping with the 'this is gonna cost you an arm and a leg', dikoting a ceramic back-and-breast clamshell is going to cost you a whole boatload of cash, because you have to dikote the whole thing. SR2 estimated a standard human-sized jacket at 1.5m2, a full suit 2.5m2, and a long coat 2.75m2. At 1000¥ per 0.1m2, you're looking at 15,000¥, 25,000¥ for a full suit, and 27,500¥ for a long coat. Not sure I agree with their estimates, but they're also talking about just the ceramics ...
Anyhow. Easy to get. Wildly expensive for what it does, for anything except very small objects, but even then there's a minimum 1000¥ charge ... unless you're doing multiple objects and adding it together.
As a preface: Please do us a favor and stop being so smug about knowing and not-knowing.
Most of what you told us in your post, barring the part about the plasma-process (which is only techno-bable anyways), can be found in the rules section in the 2050s Book down to the examples you used for armor, with the exact same types of armors and sizes used (with the difference there beingt that the sizes are written in cm², not m²).
So, yes, as a matter of fact, we (those with acces to the book) know what we are talking about, having the rules pretty much written in front of us.
Sure, its not stated explicitely that you need to coat the entire item, but when the rules give you several examples of cm² and the cost per 100 cm², the INTENT is pretty clear (at least to me).
I see where you are coming from, but i don't recognize this as a problem, except if you are bend on making it one.
For starters, First and 2nd Edition was quite a few years ago, ingame speaking.
Having a noticeable higher resistance to heat for common materials isn't really a far stretch, especially since you can now (2075) imbue even casual dresses with fire resistant coating.
"Plastic" also covers a pretty wide margin of possible materials and considering that you can nowadays (2015) print shooting-safe barrels and chambers for guns with dirt cheap consumer-grade Printers, i doubt that technological advancement (even speaking strictly INGAME from the times of 2nd to 5th) would make this a real problem.
Your "hard armor only" houserule is a ruling that has no base, even with the stuff you posted.
There is
nothing indicating in the text that it could only be applied to hard materials and seeing as both the rules text in Shadowtech and SR 2050 mention Dikote-Treated Jackets, Suits and long coats (not "Traumaplates put into your fancy clothing"), your Houserule objectively goes against RAW.
Same goes with your comment about bullets.
Why do you even mention it, when neither the Shadowtech, nor the 2050s rulebook give this as an option to begin with?
Coating Projectile weapons on the other hand, is explicitely mentioned as being possible, in the Shadowtech book, though that option is missing in the 2050 Book, same with the parrying bonus.
So:
Tl;DR:
You can coat whatever you like in Dikote, but it has to be the full object, not only parts of it (at least thats implied by both the actual rules text and the more extensive old one).
Besides that though, there are no RAW restrictions on what materials this coating can be applied on. Restricting it to "military armor" is an arbitrary Houserule.
IF you want to use the Shadowtalk as an additional source, keep in mind that its the subjective notion of a few runners on the techlevel 25 years in the ingame past.
