This is actually one of those community projects that addresses a need that the commercial world decides is too much trouble to maintain.
There will always be sources of weather data that can be decoded - but they may come and go in some cases, or at least be revised and relocated online, and there will always be a fixed interface into the simulator for these weather data packages. Because it's a flight safety issue, access to this sort of data is very likely to be open. We might lose real-time changes, but given the right sources and some inside knowledge of the structure of the data the sim needs to see, there's no reason why such a project could not massage real-world snapshots, possibly globally or at least pulled together from a variety of national sources, and format them as raw weather data, potentially for any sim. TAFs and METARs are very structured, and upper air data likewise although there if often more guesswork there due to the lack of data points and a lot of interpolation.
Obviously only METARs are any use for airport conditions, and only a few sample weather data. TAFs being forecasts are not much use. You'd also need the sources for 2000 and 5000ft winds at the very least, and a means for getting something useful out of upper air forecasts. Those wind arrows have to originate from some digital data for heading and the "feathers" for wind speeds, and if those are open sources then that can also be done.
But it would be quite an investment of time and effort to take such a project forward beyond the point of simply getting METARs and setting up airports so that the surface winds and surrounding clouds & temperatures are in the ballpark. It wouldn;t even need to be solely for FS9. Written modularized it could have a core engine and modules per weather source at the data gathering side, and modules per-sim at the data distribution side. So any and all simmers would have a stake in it.
But, away from the land of grand dreams, I might package up my .WX files and post them online in a sharing thread. You can re-use them for other flights simply by creating a copy of the .WX file and giving it the same filename as the relevant .FLT file (.WX and .FLT files always go around in pairs). Then you open the saved flight and it has adopted the weather you chose for it. Of course you can't really give them descriptive names if they're global weather. You might live in London Ontario* but be starting a flight in Jakarta.
Sim weather is am almost unreachable goal, if you want perfection.
*or London Wisconsin, West Virginia, Texas, Tennessee, Pennsylvania, Oregon, Ohio, Missouri, Minnesota, Michigan, Kentucky, Indiana, California, Arkansas, Alabama
Mpumalanga - South Africa
Limpopo - South Africa
Miranda - Venezuela
Svalbard and Jan Mayen
Altaisky krai - Russia
General Santos - Philippines
Delta - Nigeria
Kachin State - Myanmar
Kiribati
Litoral - Equatorial Guinea
Ile-de-France - France
Ontario - Canada
Orange Walk - Belize
I believe there's also one in the United Kingdom (England). It's probably not even the one that sees most rain.