How do I architecture a multilingual/multi-country network

Hello,
I am setting up an international (multi-lingual and multi-country) network of sites which offer services on a common theme (but with different methods) and will also later offer products.
Each company or individual will have one (or more) site in a multi-site setup.
I intend for viewer of the master site (our site) to be able to search very effectively through all the sites for the right service or program. Global site tags, global site search, site categories, post indexer, etc. (plus faceted search through a solar server, if possible).

My questions are:

1. I cannot imagine benefiting from global site search and tags with sites with multiple languages within the same network. Would a plugin like wpml solve the problem or should I build a network per language (or per country)... or is there any other preferred solution?

2. Can you imagine that the above-mentioned plugins will allow for a truly scalable search.

3. Can these searches and tags be confined to specific content types. For example, a tag cloud referencing all training programs and another all products? Same with global search?

4. If not, could you imagine that a plugin would be built for these specific needs?

5. Does it seem like Wordpress if the "right tool for the job" or are we likely to run into problems further down the line?

Many Thanks in advance for your answers and Our Very Best Wishes for the New Year.

Maxime.