I agree - but when you said "ALL HTML is forbidden" I went ahead and looked at the table specification part of your document and saw some things that seem rather Spartan to me. For example, the document doesn't indicate whether or not nested tables would be allowed and it doesn't seem to say how one would do bgcolor-type cell fills, or how to set border width.
There's no provision for nested tables. I don't think there's a good enough case for their necessity. Cell backgrounds and borders can be done with styles.
So if the table at http://www.wikipedia.org/wiki/Beryllium cannot be replicated pretty much as-is in wikicode then I for will have a fit (I'm sure many others will join me).
Yeah, that nested table is a nuisance. I'll have to think about that.
An alternative solution is to only allow HTML syntax to be rendered if it is in a table:namespace page.
As I said before, I want to eliminate the complexity, not just move it around. I want newbies to have some chance of being to edit the table as well as the prose around it.