I think it's a good idea, and would be a nice resource, BUT I also think the current rules are pretty clear, and that the contest runners are pretty quick to answer any questions already.
(Questions that are silly, already answered, actually legitimate, or otherwise)

I can see how some people may get confused, but we announce how it works a month or so in advance, and they have years and years of previous threads and videos to see how it works and doesn't work. Again, it may be a good idea, but I don't think it's entirely necessary. And I don't think we've had much issue with color mod mix-ups the past few contests, most of the time it's folks just plain forgetting to include it, not getting mixed up about it.

BUT, the letter mod is a much bigger issue, and a video explaining that in detail may be more profitable. After all, pikes can be 'K's, (So I was right about that...) but swords can't be 'T's, and funny looking markings on jackets may or may not count. A cursory mention of color mod stuff, with more time and detail explaining the letter mod would be much more welcome.

Also, making a custom video would be best probably, but including examples from past videos using certain tricks may also be cool. Just a thought.

As for baseplates/capes/whatnot, I'll agree. I'm not sure what the reasoning was behind banning them, but honestly it's not that hard to put the mod elsewhere. I've found that the vast majority of animators don't have any trouble including the mod whatsoever, even with the restrictions. So either way, it's that much trouble to deal with, even if it is a bit odd.

Thanks for noticing this issue and offering to help. Often people like complaining without offering any solution, and it's nice to see a more mature response to the problem at hand.

I think a forum post with still images might be better than a video because you can refer back to different parts of it more easily without rewatching the whole thing while under the gun on a THAC.

But I do agree visual aids would be a great help. I'm so used to these concepts that I rarely think about how they might confuse newcomers.

I don't think a generic video covering mod elements in both THAC and BRAWL is a good idea. While they currently share many similarities, THAC and BRAWL are definitely separate entities, run by different people, and separated by other factors, including the inclusion of outside sponsors, and the association with BiM.

A lot of your concerns and specific examples were already cleared up in the revised and updated THAC XII rules. For example, I have replaced the word "brick" with the word "piece." Also, I clearly state the parameters on what is and is not acceptable for letter mods: "The letter mod element may exist on a printed LEGO piece, but it must clearly be that letter. An eyebrow or wrinkle on a minifig’s face, or a fold in the shirt on the minifig's torso are not letters."

Other examples of clarifying rules present in THAC XII's rules that were brought up as examples in this thread:

"The blue in the color mod can be any shade of light or dark blue, even transparent. The black can only be black, not shades of gray."

"Minifig parts (for example a red torso attached to grey legs) can count as the color mod, but bricks connected to or touching baseplates do not."

"The letter may be upper or lower case, but it still must be clearly that letter. The letter can be rotated but not mirrored. Again, it must be clearly identifiable as that letter. It may be written or printed on a piece of paper or sticker, drawn directly onto a brick, printed on a piece, or built from pieces and even integrated into the set."

When I ran THAC XII it was my intention to release a guide on mod elements, probably as a series of pictures. However, I ran out of time. For THAC XIII I will have explanation pictures ready.

In conclusion, your enthusiasm for improving the clarity of the mod element rules is appreciated, but I firmly think such explanation pictures or videos should be left to the actual contest organizers.

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I did notice that video.  However, there are a few scenarios which are not covered in it.  Which is why I felt something more detailed be created.

Another reason I wanted this is that I think that the Mod Element rules should absolutely be standardized betwixt the two contests.  Having any difference would cause quite some confusion.
However, in recent times we have had some steps towards that standardization with THAC's mod rules granting the mod element be once every shot like in BRAWL rather than every single frame of the film.  It makes no sense to have the rules of the mod elements be different in each contest, not even with the slightest degree of subtlety.

One of my suggestions is not just that a guide be made, but that the rules be standardized as so that the guide is applicable to both THAC and BRAWL.  Obviously, a universal guide could not be made until such a time as the rules are standardized.  But having two separate guides, however detailed, will likely create some confusion.

As you wish.  As I said before, I do not have to make the guide myself, but was willing to do so if no one wanted to go to the trouble.

However, I do believe that it would be nice to have some degree of community involvement with some suggestions, and I really think that the people running THAC and BRAWL should come together to have these rules standardized.  Also, I think that including capes and baseplates as elements is important.

Ah, forgive me.  I was remembering the part much lower down in the post where the word brick is used as opposed to piece.  However, the word piece is at the top of the post in bold which is where it is most important.  Piece or element both work quite nicely either way.  And the use of the word brick lower down in the post is entirely unobjectionable since the word piece is used at the top.
(My suggestion for replacing the word "brick" was a minor point anyway, and not really a big issue)

A bit off topic here but still on the topic of Mod Elements.
If say, a THAC entry were to have a shot that is pixelated, hand drawn, CGI (not in brickfilm form) or something else that might make it look bad if it had a brick in it. How would we get away with doing that?
After all, someone could cheat in that by doing it before the the mod elements are allowed.

Note: halfway through typing, I though of something else. What if we included the colours in the shot themself but not in LEGO brick form. Example: mod elements red&blue can be a red shoe with blue socks inside them. Is that permitted?