Major update.

1.

I don't use the search, but why not.

2.

See point 1.

3.

See point 1.

4.

For my part, I'll say that it's not just YouTube with this nonsense; some other sites also act up periodically. On one hand, there are decent sites to bypass the problem, but on the other, not everyone knows about these sites, and using a third party for embedding code isn't exactly cool. In any case, it's worth thinking about; maybe we really can filter iFrames by YouTube if possible, or automatically rewrite malicious tags into less malicious ones (like that generator, only built into the forum).
If a tag is automatically replaced due to a forum quirk, then I think replacing it with another tag would be technically not much harder.

5.

Usually, the limit is enough for me; there's little joy in seeing signatures longer than the messages themselves, but on the other hand, it's not that terribly unbearable. Moreover, people sometimes post links to their threads, posts in factions/expansions, etc., in their signatures, and the plus from such a solution outweighs the minuses of mile-long signatures. So I'm for it.

6.

See previous point. For width, I think about 800 pixels is enough; anyway, in 2016 few weirdos are sitting with 640x480, although phone users might find it inconvenient. It's also better to introduce a height limit, otherwise some smart-aleck will post a "longcat" in their signature and that'll be fun. As for calculating the total area, I don't know; if it checks one image by area, then maybe it can sum them up, so perhaps it's a good idea, but then the limit could be larger.
As for file size, who knows—the image isn't loaded into the signature itself, it just sits on some random hosting, and I think few smart-alecks will try to pull a ten-gig monster (though I can't imagine an img tag processing a 10-gig image that is 500x500 pixels).

I'll add from myself:
7. Increase avatar size to 180x180, for example. A small thing, but it's nice.
8. Bring back ranks! Did I flood a hundred-and-fifty posts in the factions and expansions for nothing?
9. BRING BACK THE CHAT. Not that I miss our conference, and perhaps the tournament players have their own conference with utopias and fairies, but a general forum chat could be set up to more easily lure newcomers into your sections. And who knows if our factions will come back to life.
10. By the way, regarding white letters, add tags and

. The first one works via HTML, but HTML is disabled in some forum sections, and clicking a button is easier than constantly switching layouts. And the second is convenient for hiding large chunks of text to make scrolling pages easier or for all sorts of sarcastic flood comments.