I agree with the general idea but there are some details where I think your proposal goes further than is practical. Take this:
"Try to avoid jargon - but where it is particularly relevant or where it is necessary, explain all jargon clearly on the article page - a link to another article is not enough."
Taking 'jargon' to mean 'technical terms' I think this is not always practical. Is 'chromosome' a technical term? How about 'nucleotide'? I don't think it's practical to explain those terms in every single molecular biology page where they are used. If someone who doesn't understand these terms is reading the [[Polymerase Chain Reaction]] page chances are she won't understand the context anyway - even if the terms were briefly explained.
Redundant explanations make a page cluttered. Short explanations are often imprecise to the point of being wrong or not helpful. And one of the great advantage of reading Wikipedia (online) is the ability to click on technical terms for more information.
Technical terms are (usually) not just a method for ivory tower academics to keep the commoner out. They're a necessary component of the foundation of knowledge in their respective disciplines.
It's just not practical to explain everything from first principles in every single article.
Regards, Haukur