This is an interesting request, however.
The fact is that while I believe the vast majority of flightsimmers to be English conversant, there are still many who are not comfortable in English.
There are flightsimming forums in other countries, but the major sites flightsim.com, avsim.com, simviation.com cater to the English-conversant flightsimmer community.
Simflight has several non-English flightsimming forums, inlcuding Spanish. The Spanish forum is largely unattended.
http://forums.simflight.com/index.php?h=1&pf=73Rather than a new set of "foreign language forums" , maybe make the post in the language desired, with a notation in the subject (or if the subject line is in the foreign language, that would be a good hint)
If there is enough flightsim-speak in a foreign language, then maybe a specific board can be set up. This would not be a " build and they shall come" but a "come and we may build" .
The final decision (since he gets to do all the work) would be Pete's.