We encountered a significant issue while attempting to process the provided article for Watford FC. The scraped content from the Transfermarkt URL, which was expected to detail 'Watford FC U18 - Most valuable arrivals,' instead returned an error message indicating that the article content is currently unavailable.

The source page displayed messages such as 'Temporary error. Please try again.' and a prompt to 'Complete the security check before continuing.' This security measure prevented the extraction of any factual information or narrative about Watford's U18 team or their player movements.

Consequently, without any actual article text, it is impossible to fulfill the request to convert this into a strong, search-optimized bilingual article. Our SEO guidelines strictly prohibit inventing facts, dates, scores, or quotes, which would be necessary if we were to generate content without a source.

Therefore, we cannot create the 5-7 paragraphs, meta descriptions, or SEO-optimized titles for Watford based on the current input. The core requirement of adhering to the source's facts cannot be met under these circumstances.

To proceed with generating an SEO-focused article about Watford FC U18's most valuable arrivals, please provide the actual, readable article text. Once valid content is supplied, we can apply all the specified SEO optimization techniques and bilingual translation as per your instructions.