Simply use sub-directory or sub-url (whatever you call it) for each of the sites and add the language meta tag. On the index site, just use comma seperated all available language codes. However, you shouldn't use welcome pages, search engines don't like those either (nor do users) Instead, use some geoIP service to detect the country. Google uses multiple crawlers for each country.
For automatic language settings, you should do this:
Check for a language setting cookie
If unavailable, check the HTTP header for the accepted language
If that is unavailable, use geoIP.
If all the above is unavailable default to English.
Display the language selector in a corner of the website, top left or top right is best, and store the setting in a cookie.
Thanks. For the moment I will have to do with the welcome page. The company that designed the website never told me it was a problem... The next project will be to get read of it.